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Standardized Procedures for Personal Travel Surveys (2008)

Chapter: Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines

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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
×
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
×
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
×
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
×
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
×
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
×
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Suggested Citation:"Chapter 2 - Summary of Recommended Standardized Procedures and Guidelines." National Academies of Sciences, Engineering, and Medicine. 2008. Standardized Procedures for Personal Travel Surveys. Washington, DC: The National Academies Press. doi: 10.17226/13805.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

This chapter provides a summary of the recommended standardized procedures and guide- lines detailed in Chapters 4–10 of the Technical Appendix, which is published on the TRB web- site as NCHRP Web-Only Document 93. The intention is to provide a practical, stand-alone guide that can be used by agencies in designing and implementing surveys. The chapter is arranged according to the original categories used to classify the items researched in the project and also follows the chronology of the development, design, and execution of a survey: 1. Design of survey instruments (see Chapter 4 of Technical Appendix); 2. Design of data collection procedures (see Chapter 5 of Technical Appendix); 3. Pilot surveys and pretests (see Chapter 6 of Technical Appendix); 4. Survey implementation (see Chapter 7 of Technical Appendix); 5. Data coding including geocoding (see Chapter 8 of Technical Appendix); 6. Data analysis and expansion (see Chapter 9 of Technical Appendix); and 7. Assessment of survey quality (see Chapter 10 of Technical Appendix). It was not possible to recommend specific procedures for each item researched in this project because either there was insufficient information available or the amount of research required for a particular task proved to be much greater than originally anticipated. In light of this, broad guidelines were often recommended rather than specific standardized procedures. In certain cases, however, it was not even possible to recommend guidelines. Table 1 shows the type of rec- ommendation made for each item examined in this project. The following sections provide a brief description of each item and summary of the recom- mended standardized procedures and guidelines in point form. Chapters 4–10 of the Technical Appendix provide more detailed information on the methods used to determine the procedures recommended in this project. This report provides recommendations on standardized procedures and guidelines. Standards are a formal controlling process, with the requirement that they must be implemented as a min- imum requirement. If there were an agency that could take on the establishment of standards for household and personal travel surveys, then it would be a task of that agency to develop a set of standards. On the other hand, standardized procedures represent people doing the same thing consistently. There is no mandatory imposition of these; they are adopted voluntarily in the interests of improving quality, accuracy, and comparability. The purpose of this project was to identify those elements of the travel survey process that could be standardized to improve the quality, accuracy, and comparability of the results of personal travel surveys. Thus, the recom- mendations in this report are of procedures that could be adopted consistently by all those who design, develop, execute, and commission surveys to bring consistency into the way in which such surveys are done. In addition, in some areas where it was not found possible to put forward suggestions for standardized procedures, the report offers guidelines or guidance on how a par- ticular element of a person travel survey might be handled. 10 C H A P T E R 2 Summary of Recommended Standardized Procedures and Guidelines

In making these recommendations, it is also hoped that those who are less well-informed will find this to be a useful way to define how a survey might be done that would meet current expec- tations of quality, accuracy, and comparability. To this end, also, an RFP template has been developed that incorporates the majority of the suggested standardized procedures. To be con- sistent with normal RFP language, the narrative is written in prescriptive language. This should not be misinterpreted by the casual reader as implying establishment of standards; rather, it is simply a way of presenting an RFP in its normal form. 2.1 Design of Survey Instruments 2.1.1 I-1: Minimum Question Specification This item addresses the issue of the minimum question content of a household or personal travel survey. It covers what is considered to be essential information about the demographics Summary of Recommended Standardized Procedures and Guidelines 11 Categories Ref Item Type of Recommendation Section I-1 Minimum Question Specification Standardized Procedures 2.1.1 I-2 Standardization of Categories Standardized Procedures 2.1.2 Design of Survey Instruments I-5 Standard Question Wordings Standardized Procedures 2.1.3 D-1 Number and Type of Contacts Standardized Procedures 2.2.1 D-3 Proxy Reporting Standardized Procedures 2.2.2 D-4 Complete Household Definition Standardized Procedures 2.2.3 D-6 Sample Replacement Guidelines 2.2.4 D-7 Item Non-response Standardized Procedures 2.2.5 D-8 Unit Non-response Standardized Procedures 2.2.6 D-10 Initial Contacts More Research 2.2.7 D-13 Incentives Guidelines 2.2.8 Design of Data Collection Procedures D-14 Respondent Burden Standardized Procedures 2.2.9 P-2 Requirements for Pretests or Pilots Standardized Procedures and Guidelines 2.3.1Pilot Surveys and Pretests P-3 Sample Sizes for Pretests and Pilots Standardized Procedures 2.3.2 E-2 Ethics Standardized Procedures 2.4.1 E-3 Mailing Materials Standardized Procedures 2.4.2 E-4 Respondent Questions Standardized Procedures 2.4.3 E-5 Caller ID Standardized Procedures 2.4.4 E-9 Answering Machines and Repeated Call-Back Requests Standardized Procedures 2.4.5 E-10 Incorrect Reporting of Non-Mobility Standardized Procedures 2.4.6 E-11 Recording Time of Day Standardized Procedures 2.4.7 E-12 Time of Day to Begin and End Reporting Standardized Procedures 2.4.8 Survey Implementation E-13 Creation of Identification Numbers Standardized Procedures and Guidelines 2.4.9 C-1 Geocoding Standards Standardized Procedures 2.5.1 C-2 Level of Geocoding to be Performed Standardized Procedures 2.5.2 C-4 Missing Values, Use of Zero, Etc. Standardized Procedures 2.5.3 Data Coding Including Geocoding C-5 Coding Complex Variables Standardized Procedures and Guidelines 2.5.4 A-1 Assessing Sample Biases Standardized Procedures 2.6.1 A-2 Weighting and Expansion of Data Standardized Procedures 2.6.2 A-3 Missing Data Imputation Standardized Procedures 2.6.3 A-4 Data Archiving Standardized Procedures 2.6.4 Data Analysis and Expansion A-6 Documentation Standardized Procedures 2.6.5 Q-1 Computing Response Rates Standardized Procedures 2.7.1 Q-2 Transportation Measures of Quality Standardized Procedures 2.7.2 Q-3 Coverage Error Standardized Procedures 2.7.3 Q-5 Proxy Reporting as a Quality Indicator Standardized Procedures 2.7.4 Q-6 Validation Statistics Standardized Procedures 2.7.5 Q-7 Data Cleaning Statistics Standardized Procedures 2.7.6 Q-8 Number of Missing Values Standardized Procedures 2.7.7 Assessment of Survey Quality Q-9 Adherence to Quality Guidelines Standardized Procedures 2.7.8 Table 1. Summary of items examined in project.

of the household and its members, the attributes of the vehicles owned, and the attributes of the travel and activities that are recorded by household members. Based on the discussion in Section 4.1 of the Technical Appendix, the recommended mini- mum question specifications are shown in Table 2. These represent the minimum set of ques- tions recommended in all future household travel surveys. Additional questions may be asked in many surveys, however. For example, income is not included for reasons that are discussed in Section 4.1 of the Technical Appendix. Many recent surveys would not conform to this specifi- cation, which is also indicative of the problems of comparability and completeness in current surveys. 2.1.2 I-2: Categories for Minimum and Other Questions For the minimum questions suggested in the preceding question, a number are subject to con- siderable variability in the categories that might be used to record the data. Proposing a set of standardized categories for those questions and also for one or two other questions that are likely to be included in many surveys would seem useful in pursuing the goal of improving compara- bility, accuracy, and quality. The variables selected for standardization of categories are type of dwelling (H2), relationship (H4), housing tenure (H7), education level attained (P10), disability (P11), race (P12), vehicle body type (V1), vehicle ownership (V5), trip purpose (A2), means of 12 Standardized Procedures for Personal Travel Surveys Category Ref. Item Description H1 Location Home address or home position in geographic terms H2 Type of Building Detached, semi-detached, terraced, flat, etc. H3 Household Size Number of household members H4 Relationships Matrix of relationships between all members of the household H6 Number of Vehicles Summary of number of vehicles from vehicle data H7 Housing Tenure Own or rent status Household H8 Re-contact Willingness to be contacted again for further surveys, etc. P1 Gender P2 Year of Birth (Preferable to requesting age) P4 Paid Jobs Number of paid positions and hours worked at each in the past week P6 Job Classification Employee, self-employed, student, unemployed, retired, not employed, etc. P7 Driving License Whether a current drivers license is held P8 Non-mobility Indication of why no out-of-home activity was performed on a survey day including work-at-home days P10 Education Level Highest level of education achieved P11 Disability Types of mobility disability, both temporary and permanent P12 Racea Defined as currently measured in the U.S. Census Personal P13 Hispanic Origin Defined as currently measured in the U.S. Census V3 Body Type e.g., car, van, RV, SUV, etc. V4 Year of Production V5 Ownership of Vehicle Household/person, lease, institution Vehicle V6 Use of Vehicle Main user of vehicle A1 Start Timeb A2 Activity or Purpose A3 Location Where the activity was performed, unless traveling A4 Means of Travel If activity is travel, what mode(s) was used (including specifying if a car passenger or driver) A5 Mode Sequence Unless collected as fully segmented data A6 Group Size Number of persons traveling with respondent as a group A7 Group Membership Number of persons in the group who live in respondent’s household A8 Costs Total amount spent on tolls, fares, and respondent’s share Activity A9 Parking Amount spent to park a All surveys would use the U.S. Census Bureau definition of Race and Hispanic Origin. b Only start time needs to be ascertained in a time-use or activity survey because, by definition, the start time of an activity is the end time of the previous activity. Only the last activity should need an end time. In a trip-based survey, start and end time should be included. Table 2. Recommended minimum question specifications.

travel (A4), fuel type, and employment status. Most of the other questions either do not require categories or the categories are self evident and already standardized (e.g., gender [P1]). More details concerning this issue are to be found in Section 4.2 of the Technical Appendix. To devise recommended standardized categories, definitions of seven international statistical agencies for the specific variables were looked at and compared with the seven data sets exam- ined as well as two other survey definitions. The results are shown in Table 3. Where less detail is desired, the primary categories are recommended to be used and these should suffice in the majority of surveys; where more detail is required, the secondary categories should be used. It is also possible to selectively add secondary categories—for example, housing tenure might be used with Categories 1, 2, 31, and 32, if the additional level of detail were desired only for Category 3. Similar mixing of category levels could be used with any of the variables in Table 3—for exam- ple, splitting rail (A4-71) into different submodes in an area such as New York may be desirable. Standardization of the activities to be included in designs that provide an activity list would also be useful and has been requested by some professionals involved in transportation surveys. The grouping of activities into common trip purpose–related categories would also be a useful element of this aspect of standardization. This is addressed in Section 2.5.4. 2.1.3 I-5: Standard Question Wordings To permit comparisons across surveys conducted in different locations at different times, it is essential that certain key questions be asked in the same manner. It is also important that the question wording or response definitions in a local survey be consistent with the wording (and definitions) used in a national survey or census, especially for variables that may serve as the basis for sampling, expansion, and checking for bias. Again, the focus of this issue is the mini- mum questions proposed in Section 2.1.1, but with the addition of some other questions that are frequently used in travel surveys, such as income. Only those questions where the wording is not necessarily self-evident and where variations that could affect the responses given are offered for standardization in Table 4. Details on this issue are provided in Section 4.3 of the Technical Appendix. 2.2 Design of Data Collection Procedures 2.2.1 D-1: Number and Type of Contacts This issue relates to the number of times and the manner in which households should be con- tacted to obtain complete household responses. In terms of recruitment, the question arises as to the number of times a household should be contacted to obtain a complete recruitment response, especially if initial contact results in the household requesting to be called back or sim- ply a non-contact (answering machine, busy, and modem/fax). Analysis conducted as part of this project and results from previous studies (which are described in Section 5.1 of the Techni- cal Appendix) indicate that there is no significant reduction in non-response bias if more than six attempts are made to call a household during either recruitment or retrieval. There are also no real changes in the conversion to complete interviews for households that requested to be called back or that were not contacted initially. The following standardized procedures are recommended to be followed: 1. A survey should include the use of reminders, which should be planned and programmed in the initial stages of the survey. The form of the reminders will depend on the methods used for the survey. However, some mix of telephone, mail, and e-mail reminders would nor- mally be appropriate. Summary of Recommended Standardized Procedures and Guidelines 13

14 Standardized Procedures for Personal Travel Surveys Variable Primary Category Code Secondary Category Code Single family house detached 1 Single family house detached 10 Townhouse 21 Row house 22 Duplex 23 Triplex/fourplex 24 Single family house attached 2 Apartment/mother-in-law suite 25 Condominium 31 Apartment/condominium 3 Rented apartment 32 Mobile home 41 Mobile home/trailer 4 Trailer/camper 42 Dormitory 51 Hostel 52 Nursing home 53 Dorm/group quarters 5 Military barracks 54 Hotel/motel 6 Hotel/motel 60 Type of Dwelling (H2) Other 9 Other 90 Self 1 Self 10 Husband/wife 21 Spouse/partner 2 De facto husband/de facto wife 22 Natural son/daughter 31 Adopted son/daughter 32 Stepson/stepdaughter 33 Son/daughter 3 Son-in-law/daughter-in-law 34 Natural father/mother 41 Adopted father/mother 42 Stepfather/stepmother 43 Father/mother 4 Father-in-law/mother-in-law 44 Relationship (H4) Brother/sister 5 Natural brother/sister 51 Adopted brother/sister 52 Stepbrother/stepsister 53 Brother-in-law/sister-in-law 54 Paternal grandfather/grandmother 61 Grandfather/grandmother 6 Maternal grandfather/grandmother 62 Grandson 71 Grandchild 7 Granddaughter 72 Male 81 Other relative 8 Female 82 Boarder 91 Housemate/ room mate 92 Not related 9 Other non-relative 93 Owned with mortgage 11 Own 1 Owned without mortgage 12 Rent paid 21 Rent 2 Occupied without rent 22 Provided by job 31 Housing Tenure (H7) Provided by job/military 3 Provided by military 32 No school completed 1 No school completed 10 Preschool/nursery 21 Elementary school 2 Kindergarten–4th grade 22 5th–8th grade (junior high) 31 9th–12th grade (no diploma) 32 High school 3 High school diploma 33 Some college but no degree 41 Associate degree in college 42 College/university 4 Bachelor’s degree 43 Some graduate school, no degree 51 Master’s degree 52 Professional school degree 53 Education Level (P10) Post graduate studies 5 Doctorate degree 54 Difficulty standing 1 Difficulty standing 10 Difficulty climbing 2 Difficulty climbing 20 Visually impaired/blind 3 Visually impaired/blind 30 Hearing impaired/deaf 4 Hearing impaired/deaf 40 Require wheelchair 5 Require wheelchair 50 Require cane/walker 6 Require cane/walker 60 Disability (P11) Other (specify) 9 Other (specify) 90 Table 3. Recommended standardized categories.

Summary of Recommended Standardized Procedures and Guidelines 15 Variable Primary Category Code Secondary Category Code White (alone) 1 White (alone) 10 Black/African American (alone) 2 Black/African American (alone) 20 American Indian 31 American Indian/Alaskan Native (alone) 3 Alaskan Native 32 Asian Indian 41 Chinese 42 Filipino 43 Japanese 44 Korean 45 Vietnamese 46 Asian (alone) 4 Other Asian 47 Native Hawaiian 51 Guamanian or Chamorro 52 Samoan 53 Native Hawaiian or Pacific Islander (alone) 5 Other Pacific Islander 54 Some other race (alone) 6 Some other race (alone) 60 Race (P12) Two or more races 7 Two or more races 70 Auto 1 Auto 10 Vehicle Body Type (V1) Van 2 Van 20 Recreational vehicle (RV) 3 Recreational vehicle (RV) 30 Utility vehicle 4 Utility vehicle 40 Pick-up truck 5 Pick-up truck 50 Other truck 6 Other truck 60 Motorcycle 7 Motorcycle 70 Other (specify) 9 Other (specify) 90 Household member owned or leased 1 Household member owned or leased 10 Employer owned or leased 2 Employer owned or leased 20 Vehicle Ownership (V5) Other (specify) 3 Other (specify) 30 Home – domestic activity 10 Home 1 Home – paid work 11 Main job 21 Other job 22 Volunteer work and community services 23 Work and work-related 2 Looking for work 24 Attendance at childcare 31 Attendance at school 32 Education/childcare 3 Attendance at college 33 Restaurant/café 41 Fast food 42 Eating out 4 At friends’ home 43 Availing of/shopping for administrative services 51 Availing of/shopping for professional services 52 Availing of/shopping for government/public services 53 Availing of/shopping for personal services 54 Personal business/medical 5 Availing of/shopping for medical and health care services 55 Trip Purpose (A2) Purchasing food and household supplies (groceries) 61 Purchasing clothes, shoes, personal items 62 Purchasing household appliances, articles, equipment 63 Purchasing capital goods (cars, houses etc.) 64 Comparison shopping 65 Shopping 6 Window shopping 66 Communication/ correspondence 71 Socializing activities 72 Participating in religious/community/cultural events/activities 73 Visiting entertainment and cultural venues 74 Indoor and outdoor sporting activities 75 Games/hobbies/arts/ crafts 76 Social/recreational 7 Print/audio/visual media 77 Table 3. (Continued). (continued on next page)

16 Standardized Procedures for Personal Travel Surveys Variable Primary Category Code Secondary Category Code Accompanying children to places 81 Accompanying adults to places 82 Accompanying others/travel related 8 Pick up or drop off other people/get picked up or dropped off (private car, car/van pool, shuttle/limousine) 83 Activities related to bus, public transit and group rides (except car/van pool and shuttle/limousine) 84 Change travel mode 85 Other (specify) 9 Not further defined (n.f.d.) 90 Car driver 11 Van driver 12 Car/van/truck driver 1 Truck driver 13 Car passenger 21 Van passenger 22 Car/van/truck passenger 2 Truck passenger 23 Motorcycle 31 Moped 32 Motorcycle/moped 3 Scooter 33 Bicycle 4 Bicycle 40 Walk 51 Skate/roller skate/ roller board 52 Motorized wheelchair 53 Walk/wheelchair 5 Non-motorized wheelchair 54 Regular bus 61 Intercity bus 62 Express bus 63 Bus/school bus 6 School bus 64 Train 71 Train 7 Trolley/streetcar 72 Taxi 81 Shared-ride taxi/jitney 82 Commuter van/shuttle bus: employer paid 83 Commuter van/shuttle bus: pay fare 84 Dial-a-Ride 85 Taxi/shuttle 8 Shuttle/limousine 86 Means of Travel (A4) Other (specify) 9 Other (specify) 90 Gasoline 1 Gasoline 10 Diesel 2 Diesel 20 LPG/LNG 3 LPG/LNG 30 Dual Fuel 4 Dual Fuel 40 Fuel Type Other (specify) 9 Other (specify) 90 35–45 hours 11 46–55 hours 12 Full-time 1 Greater than 56 hours 13 Less than 20 hours per week 21 Part-time 2 Greater than 20 hours per week 22 Retired 31 Retired 3 Semi-retired 32 Full-time homemaker 4 Full-time homemaker 40 Unemployed seeking employment 5 Unemployed seeking employment 50 Unemployed not seeking employment 6 Unemployed not seeking employment 60 Full-time student 7 Full-time student 70 Child not in school/infant*to be specified if skip mechanism not in place 8 Child not in school/infant*to be specified if skip mechanism not in place 80 Employment Status Volunteer work (unpaid) 9 Volunteer work (unpaid) 90 Table 3. (Continued).

2. A schedule of contacts and reminders, based on Table 5, should be put in place for a house- hold travel survey, at least up to Step 6. The use of the reminders to Step 11 should be rec- ommended except where response rates have already fallen below the point of cost effec- tiveness for further reminders. 3. The number of attempts to call back to a household that is not reached on the first call or where a request is made for a call back should be limited to five (i.e., a maximum of a total of six calls made to a household). These call-back attempts should be made at different times on dif- ferent days of the week. This would apply separately to the initial attempt at recruitment and to the attempt to retrieve data. 2.2.2 D-3: Proxy Reporting In surveys that use telephone or personal interviews as the method to retrieve completed data, there is a continual issue regarding who provides the activity or travel information: the person performing the activity or travel (direct respondent) or someone else. Those instances in which Summary of Recommended Standardized Procedures and Guidelines 17 Question Recommended Question Wording Household Size (H3) “Including yourself, how many people live at this address? Please do not include anyone who usually lives somewhere else or is just visiting, such as a college student away at school. (If further clarification is needed, include infants and children, live-in domestic help, housemates, roomers.)” Number of Vehicles (H6) “How many vehicles are owned, leased, or available for regular use by the people who currently live at this address? Please be sure to include motorcycles, mopeds and RVs.” (As clarification, regular use means “are in working order.”) It is recommended that travel surveys include a separate question regarding the availability of bicycles for daily travel: “How many bicycles in working condition are available to members of your household for use in their daily travel?” Owner or Renter Status (H7) “Do you own or rent your home? 1 Own/buying (e.g. paying off a mortgage) 2 Rent/lease or 3 Provided by job or military” Gender (P1) “Are you (is this person) male or female?” Disability (P11) A question should be asked about disabilities that impact travel. “Do you have a disability or condition that has lasted 6 or more months and which makes it difficult to go outside the home alone—for example, to shop or visit a doctor’s office?” Activity or Trip Purpose (A2) For work or work-related activities: Volunteer work should be specifically excluded from the definition; The clarification should be added that work means work for pay or profit; and, Questions should be asked about a second job. When asking for activities, at a minimum include a category “Other at-home activities.” Advanced practice is to ask separately for activities that could be performed either at or away from home, such as meals, work, shopping (using the Internet). Number in Traveling Party (A6) “Including yourself, how many people were traveling with you? How many of these were household members?” If computer-assisted telephone interviewing (CATI ) is used, it is suggested that the follow-up question regarding number of household members only be asked when the household size is greater than one. At a minimum, the number in the traveling party should be asked whenever a private car, van, or truck is the mode of travel. Income “Please stop me when I get to the category that best describes the total combined income for everyone living at this address for last year:” Income response categories should match the start and end points used by the U.S. Census, although collapsing across income categories is acceptable. See Section 2.5.4. Table 4. Recommended standardized question wordings.

18 Standardized Procedures for Personal Travel Surveys the activities or travel are reported by someone other than the person who actually performed the activity are referred to as having been reported by “proxy.” There is a relatively large body of research that concurs that the number of trips is lower when reported by proxies. Analysis of this issue is reported in detail in Section 5.2 of the Technical Appendix. It is recommended that all surveys, at a minimum, establish the following policies with regard to proxy reporting: 1. For all persons, include a code for whether the activity/travel report was provided directly by the individual conducting the activities or travel, or by a proxy. 2. For persons aged 14 and under, require parental or other adult proxy reporting. 3. For persons aged 15 to 17, permit proxy reporting unless the individual is available to report their activities directly with parental permission. 4. All persons aged 18 or older should be asked directly for their activities or travel. 5. The survey methods report should include the percent of adult respondents (persons aged 18 or older) whose activities or travel were reported by proxies (regardless of whether a completed diary was available), excluding from the denominator persons who were phys- ically or mentally unable to provide direct reporting at the time of retrieval (illness, inca- pacitation, etc.). See also Section 2.7.4. 6. Establish a calling protocol that requires at least one call back attempt to obtain a direct report from each adult household member aged 18 or older. Once sufficient surveys have been conducted using these guidelines, it may be possible to develop factors to adjust for under- or over-reporting by proxies of certain types of trips. 2.2.3 D-4: Complete Household Definition The definition of what is a complete household is important because it determines when the sample size specified for a survey is met. There is considerable variability in what has been used as the definition in past household travel surveys: some surveys specifying that every member of the household must complete travel information and personal details for the household to be considered complete, while others specify that only 50% of household members have to com- plete the survey for the household to be considered complete. There are important trade-offs in this. The more stringent definitions will lead to many households being excluded, especially large Step Day Contact Type Content Received by Household 1 Advance letter (R – 7) Mail Pre-notification letter A week before recruitment is scheduled to commence 2 Recruitment (R) Telephone Recruitment interview Recruitment day 3 R+1 Mail Survey package sent out R+3 to R+5 4 Day before diary day (D – 1) Telephone Pre-diary day reminder (motivation call) D-1 5 D+1 Telephone Reminder to return completed survey (motivation call) D+1 6 D+2 Mail Postcard reminder/reset of diary day to D+7 D+4 to D+6 7 D+6 Telephone Reminder and check on second opportunity for diary day D+6 8 D+9 Mail Postcard reminder and reset of diary day to D+14 D+11 to D+13 9 D+13 Telephone Reminder and check on third opportunity for diary day D+13 10 D+15 Mail Re-mailing of survey package and reset of diary day to D+21 D+17 to D+19 11 D+20 Telephone Reminder and check on fourth opportunity for diary day D+20 Table 5. Recommended schedule of contacts and reminders.

Summary of Recommended Standardized Procedures and Guidelines 19 households, with potential sample biases arising. On the other hand, too lenient a definition will likely result in poor estimation of household travel. Further discussion of this is to be found in Section 5.3 of the Technical Appendix. The following standardized procedures are recommended: 1. At least key household, person, and vehicle information be obtained. In other words, the minimum set of questions outlined in Section 2.1.1 of this report should be answered for a household response to be considered acceptable or valid. Other key information may also be required for the response to be considered complete, but this is dependent on the spe- cific objectives of the survey. 2. At least an adult from every age group represented in the household, as well as younger household members if eligible, should complete the trip/activity data items specified in Sec- tion 2.1.1. These age groups may be the following: • 15–17 (if household members under the age of 18 are eligible), • 18–64 years, • 65–74 years, and • over 74 years. 3. For the last three age groups, proxy reports should not count towards determining com- pleteness of the household. 4. Partial responses should not be eliminated from the data set. Partial information can be useful and these households may be re-contacted in various follow-up exercises. Complete person information from incomplete households can be used in various applications. Also, it is a waste of resources to remove households from the data set. This is important given increasing survey costs. 2.2.4 D-6: Sample Replacement Refusals result in lost sample and require some sample make up or replacement. Procedures for sample replacement are critical in preserving the integrity of the initial sample. Two questions arise: 1. When should a sampled household or person be considered non-responsive and a replace- ment make-up household or person be selected? 2. How should replacements for the sample be provided? Detailed discussion of this issue is to be found in Section 5.4 of the Technical Appendix. The following standardized procedures are recommended: 1. Conduct a pilot survey. A pilot survey should be conducted to enable the estimation of the expected non-response rate. This will help with developing the required sample size. (See also Section 2.3.1 of this report.) 2. Draw a large initial sample. To overcome unanticipated sample loss, it is suggested that the initial sample that is drawn be much larger than the final required sample, taking into account the expected non-response rate, and then increasing beyond this to allow for unforeseen problems. 3. Preserve the draw order of numbers. The order in which numbers are drawn needs to be pre- served and contact made strictly in that order. For example, for a random digit dialing (RDD) list, numbers listed later in the list should not be recruited before numbers listed earlier in the list have either been recruited or discarded. 4. Create additional sample. If using RAND (RAND Corporation, 1955) random numbers, additional sample may be created and drawn after the initial sample has been exhausted. If using RDD lists, this should not be done because the two random samples will not be related and bias may be introduced.

20 Standardized Procedures for Personal Travel Surveys 5. Conduct refusal conversion. Refusal conversion should be conducted, with a maximum of five attempts to convert initial soft refusals. This recommendation is also stated for initially non-contactable households and is shown in Section 2.2.1 of this report. 2.2.5 D-7: Item Non-Response Item non-response has been defined as either the failure to obtain an answer to a specific ques- tion or the failure to obtain a true and complete answer. Thus, item non-response occurs not only as a result of data being missing but also when incorrect data are provided. Invalid data are data items whose values are beyond the possible or feasible range of that item. Inconsistent data are data items whose values are inconsistent with the values of other data items of the respondent. Item non-response is closely linked to several other items discussed in this report. First, it is linked to the definition of a complete household addressed in Section 2.2.3 because it is only when item non-response is within tolerable limits that a responding household is considered complete. Second, it relates to survey design and survey execution because the form in which the questions are posed and the manner in which the survey is conducted are known to have a sig- nificant impact on item non-response. A more detailed discussion of this issue is to be found in Section 5.5 of the Technical Appendix. The overall approach should be that item non-response should be minimized by good survey design and good survey execution. To achieve this, the following standardized procedures are recommended: 1. For CATI, computer-assisted personal interviewing (CAPI), and Internet surveys, admin- istration of the survey should be programmed to require that a response is obtained on each item. 2. Mail-back surveys should be edited immediately upon receipt so that respondents can be re-contacted to query missing or incorrect data items while the survey is still fresh in their memory. 3. Item non-response should be considered to include items where values are missing, where the respondent has indicated that they “don’t know,” and where the respondent has refused to answer. 4. An overall estimate of item non-response should be obtained from the level of non- response on each of the following items: • Travel mode; • Driver license status; • Start time and end time of trip or travel time of trip (if only travel time of trip is reported); and • Vehicle occupancy. A statistic, which is the average item non-response among the above items, should be used as the overall measure of non-response in the data and should be expressed as a percentage. 2.2.6 D-8: Unit Non-Response There are two broad categories of unit non-response: refusals (hard refusals, soft refusals, and ter- minations) and non-contacts (for CATI surveys, these are busy, no reply, and answering machines). High rates of unit non-response are generally associated with non-response error. Non-response error is a function of the non-response rate and the difference between respondents and non- respondents on any statistic of interest. A lower unit non-response rate is desired because this reduces the incidence of non-response bias. This issue is discussed at length in Section 5.5 of the Technical Appendix, together with the results of a non-response survey conducted as part of this research.

Unit non-response is a significant and growing problem in household travel surveys. A num- ber of standardized procedures and guidelines are recommended as a means to attempt to reduce this phenomenon. Some of these overlap or duplicate those found elsewhere in this report. The following standardized procedures are recommended: 1. Use pre-survey monetary incentives. The positive effect of incentives has been clearly demonstrated in the research reviewed and undertaken here. In contrast to the findings of Section 2.2.8, it appears that larger incentives may be required to convince those who usually refuse or terminate the survey to complete it. This may require a second round of attempts to convert non-responders to responders in which a higher incentive is offered to induce conversion. 2. Use a pre-notification letter and reminders. Special care is required in formulating the pre- notification letter so that it is simple in language, appealing to a wide range of people, and clearly sets forth the importance of responding. Care must also be taken in determining who should sign the letter and in the affiliations shown in the letterhead used. 3. Special train interviewers. Where interviewers are used, special training of interviewers has been shown to have substantial effects on response. Therefore, considerable effort should be paid to developing thorough and complete training of interviewers. 4. Increase efforts to contact households that are difficult to contact. This may be done by increas- ing the number of calls for non-contacted units, designating specific times to call non- contacted units, expanding the data collection period, and conducting face-to-face interviews. 5. Undertake non-response surveys. Non-response surveys should be undertaken as a standard ele- ment of all household travel surveys, rather than as the exception that is the present situation. The following guidance is also offered, based on the research undertaken on this topic: 1. Efforts should always be undertaken to reduce respondent burden in the design of any survey. This often has more to do with the ease with which people can complete the survey task than the actual length of the survey per se. 2. Shorter surveys should be used wherever possible. This raises difficult issues as the need for more detailed data emerges in the transportation profession. Pilot surveys offer a useful mechanism for testing alternative designs, and focus groups should also be used in the design process to determine how to make a survey design shorter while still being effective. 3. Options should be provided on how and when to respond. These options appear likely to increase the number of terminators who will complete the survey. However, more research is needed on the effect of mixed-mode surveys. 2.2.7 D-10: Initial Contacts The subject of this section is the first contact made with a potential respondent in a survey. Contact can be by telephone, mail, e-mail, or possibly even personal interview. In telephone surveys and personal interviews, it involves the very first few words uttered following contact with a prospective respondent. When the initial contact is by mail, it is the envelope in which the material is mailed, the documentation in the envelope, and the opening sentence on the cover letter. The primary need is to design the introduction to surveys in such a fashion that refusals are avoided as much as possible. Currently, the proportion of refusals that occur during initial con- tact is surprisingly high. The factors that influence the rate at which people hang up seem to have received relatively little research in the past. Further discussion of this is to be found in Section 5.7 of the Technical Appendix. Standardized procedures on script formulation would be advantageous in limiting the grow- ing trend in hang ups with telephone surveys. However, further research is required before any Summary of Recommended Standardized Procedures and Guidelines 21

22 Standardized Procedures for Personal Travel Surveys standardized procedures or guidelines can be recommended in this area. It is suggested, how- ever, as an interim procedure that the opening statement on the telephone should 1. Be as brief as possible; 2. State as early as possible that it is not a marketing call; and 3. Start with the words “Hello, this is __________ . . .” rather than “Hello, my name is _________ . . . ,” the latter of which seems to signal that it is probably a marketing call. 2.2.8 D-13: Incentives Incentives are offered in some surveys to induce respondents to complete the survey. Many surveys do not offer incentives, but among those surveys where incentives are offered, consider- able variability in type and magnitude are found. There is considerable difference of opinion among transportation professionals as to whether incentives should be offered. There is also substantial diversity in what is offered for an incen- tive. Incentives have ranged from a gift to a significant payment of money ($10 and more per household, particularly for GPS surveys, where incentives as high as $50 have been offered). Some are offered only to those completing the survey, while others are offered to all potential respondents. The extent of current information about the use of incentives generally and in per- sonal travel surveys particularly is provided in Section 5.8 of the Technical Appendix. Several recommendations are offered for standardized procedures on this topic: 1. Incentives should be offered in all personal travel surveys unless a pilot survey is able to demonstrate clearly that a final response rate in excess of 70% can be achieved without any incentive. 2. Incentives should be offered only as pre-completion incentives—that is, they are offered to all recruited units of the sample and are not offered in return for respondents returning a completed survey. 3. Incentives should be indicated as being provided for completing the survey task, but not conditioned on a return being received. 4. Incentives should be monetary in form except where local laws or ordinances prohibit offering money. In such cases, a small gift should be offered. 5. Monetary incentives should generally be small and on the order of $1–$2 per person except in cases where attempts are being made to obtain responses from those who typically fail to respond to a survey. In the latter case, a larger incentive may be worthwhile. 6. Incentives should be offered to each individual and not to the household as an entity. 7. Entry into a sweepstakes, provision of lottery tickets, and other similar forms of incentives are not recommended. The literature does not provide support that such incentives are effective. It is recommended that alternative incentives be tested, whenever possible, in a pilot survey to establish whether a particular population will be responsive to specific incentives. Such tests may compare alternative monetary levels, as well as comparing between a gift and money, although existing tests of gifts versus money have clearly shown the supremacy of money. 2.2.9 D-14: Respondent Burden Respondent burden is both tangible and intangible. In tangible terms, it can be measured as the amount of time, cost, etc., that is involved in a respondent complying with the requests of a survey. It could also be measured in terms of the number of times a respondent is contacted and asked to provide information. The intangible aspects of respondent burden are much less easily measured and may be subsumed under the general title of perceived burden. There is general agreement that efforts should be made to reduce the data collection burden for respondents to travel surveys. There is less agreement as to what constitutes respondent bur-

Summary of Recommended Standardized Procedures and Guidelines 23 den, and how reductions in burden may be achieved. Respondent burden is examined in Sec- tion 5.9 of the Technical Appendix. It is recommended that an estimate of measured respondent burden be routinely reported as part of any travel survey method documentation. This estimate should include the actual or esti- mated time in minutes for • Review of printed materials, including instructions. • Recordkeeping (as applicable to survey design). • Use of “memory jogger” to record trips. • Recording odometer readings from household vehicles. • Actual average call time for (as applicable) – Recruitment; – Reminder; – Retrieval; and – Other calls (verification, re-contact for incomplete data, odometer readings, etc.). • Completing diaries and other requested data (mail-back or Internet). • Gathering the completed surveys from responding household members. • Mailing the surveys back to the survey firm/sponsoring organization (if applicable). To permit comparisons across surveys, it is recommended that the measured respondent bur- den be reported at the household level, using the average number of persons per household to factor person-level response times to an estimate for the entire household. 2.3 Pilot Surveys and Pretests 2.3.1 P-2: Requirements for Pretests or Pilot Surveys Pretests and pilot surveys are the process of testing various aspects of the survey design, proto- col, instruments, analysis, etc., on a small sample of the population prior to fielding the main sur- vey. The intention of pretests and pilot surveys is to determine whether everything in the intended survey will work and produce the expected results. In some instances, pretests or pilot surveys may be conducted to compare two or more methods for some element of the survey process and to determine which to choose. In other cases, there is no comparison test involved, although it may be anticipated that some refinements to elements of the survey process will result. Further elabo- ration on pretests and pilot surveys can be found in Section 6.1 of the Technical Appendix. It is recommended that the terms pilot survey and pretest be defined as follows: 1. Pilot Survey—a complete run through or dress rehearsal of the entire survey process, including drawing the sample, conducting the survey, coding the data, and performing basic analysis of the data. A pilot survey is conducted on a small sample of the same popu- lation that will be sampled for the main survey. As distinct from a pretest, the pilot survey involves a test of every element of the main survey, conducted in exactly the same way as is planned for the main survey. A pilot survey may also be used to test two or more different survey procedures and compare the results in order to assist in selection of one for the main survey. In such a case, each version to be tested is subjected to every step of the main survey. 2. Pretest—a test of any element, or sequence of elements of a survey, but comprising less than the full survey execution. For example, the instrument may be pretested by having a small subsample of respondents complete the instrument and then reviewing limited aspects of the completed instruments to determine whether any design changes are war- ranted. Any aspect of survey design and implementation may be subjected to a pretest. Pretests may also be used to compare alternatives for an element or elements of a survey. The main distinction between a pretest and a pilot survey is that pretests do not involve testing all aspects of the planned main survey, but may be limited to subsets of the protocol,

24 Standardized Procedures for Personal Travel Surveys instrument, sampling, etc. During the design phase, several sequential pretests could be conducted to test various refinements of the instrument, protocol, sampling, etc. Second, it is recommended that one or more pretests and/or one or more pilot surveys should be an essential step in all transportation surveys unless there are specific circumstances that ren- der such a step unnecessary and unlikely to produce useful information. It is further recommended that the following guidelines with respect to pilot tests and pretests be adopted: 1. In any survey in which interviewers will interact with respondents, the pilot survey or pretest should include listening in to interviewers to determine how they interact with potential respondents, how well they keep to the script of the survey, and whether the script causes difficulties in conversational style. 2. In any survey that uses interviewers or observers, there should be a debriefing with those used in the pilot survey or pretest to determine whether difficulties were experienced in handling survey procedures, questionnaires or other materials, scripts, etc. 3. If it has been 10 years or more since the last time a survey was done, a pilot survey should always be undertaken because the changes in population that will have occurred will ren- der any past experience irrelevant. 2.3.2 P-3: Sample Sizes for Pretests and Pilot Surveys Because we recommend that pretests and/or pilot surveys be conducted in all future travel sur- veys, it is appropriate to establish the required sample size of these initial tests or surveys. For further discussion, the reader is referred to Section 6.2 of the Technical Appendix. It is recommended that the following standardized procedures be adopted by the profession: 1. Whenever possible, the main sample should be drawn first and the pilot survey or pretest sam- ple drawn only from those households or persons who were not drawn for the main sample. When the pilot survey or pretest is being conducted to determine the sample size required for the main survey, two options are possible. The first option is that a main sample can be drawn that is expected to be more than sufficient in size. The pilot survey or pretest sam- ple can then still be drawn subsequently from those households or persons who will not be included in the main sample under any likely circumstances. The second option is to draw the pilot survey or pretest sample at random from the total population and then be sure to exclude all such drawings from the population for drawing the main sample. The former of these two is the preferred method. 2. No pretest or pilot survey should use a sample of less than 30 completed households or respon- dents. Exercises using smaller samples than this should be regarded as preliminary tests and pre-pilot surveys and should always be followed by a pretest or pilot survey with at least a 30 respondent sample size. 3. The minimum sample sizes shown in Table 6 should be used in all pilot surveys and appropri- ate pretests. 2.4 Survey Implementation 2.4.1 E-2: Ethics Ethics describe minimum acceptable standards of conduct or practice. In travel surveys, this relates to how a survey agency conducts itself with respect to those interviewed, the client, any subcontractors, and the public as a whole. It also relates to a survey agency’s actions following the data collection process when data are cleaned, coded, analyzed, and archived.

Summary of Recommended Standardized Procedures and Guidelines 25 Ethics reflect what all stakeholders may consider “fair” or “reasonable” conduct by those involved. In practical terms, the application of ethics involves implementation of precautions to protect those affected from adverse effects. Ethics protect the rights of individuals and groups and serve to reduce public disapproval and criticism of what is done. A review of the ethics standards used in various other areas of surveying is provided in Sections 2.2.2 and 7.1 of the Technical Appendix. After reviewing documents prepared by various associations on different aspects of ethical conduct in the execution of travel surveys, it is recommended that the following ethical conduct be observed in all future travel surveys: 1. The anonymity of the persons surveyed, and the confidentiality of the information they provide, must be protected at all times; 2. A survey respondent may not be sold anything or asked for money as part of the survey; 3. Persons must be contacted at reasonable times to participate in the survey and must be allowed to reschedule participation in the survey to a different time if that is more con- venient for them; 4. Survey personnel must be prepared to divulge their own name, the identity of the research company they represent, the identity of the agency that commissioned the study, and the nature of the survey being conducted, if requested by a respondent; 5. Children under the age of 15 may not be interviewed without the consent of a parent or responsible adult; 6. A respondent’s decision to refuse participation in a survey, not answer specific questions in the survey, or terminate an interview while in progress must be respected if that is the respondents’ firm decision; 7. Respondents may not be surveyed or observed without their knowledge: methods of data collection such as the use of hidden tape recorders, cameras, one-way mirrors, or invisible identifiers on mail questionnaires may only be used in a survey if the method has been fully disclosed to the respondent and the respondent agrees to its use. Table 6. Sample sizes required for specified levels of accuracy. Measure Assumed Value Desired Accuracy Sample Size Measure Assumed Value Desired Accuracy Assumed Variance Sample Size 50% ±5% 384 10 ±1 100 384 50% ±10% 96 10 ±2 100 96 50% ±15% 43 10 ±3 100 43 50% ±20% 24 10 ±4 100 24 60% or 40% ±5% 369 10 ±1 50 192 60% or 40% ±10% 92 10 ±2 50 48 60% or 40% ±15% 41 10 ±3 50 21 60% or 40% ±20% 23 10 ±4 50 12 75% or 25% ±5% 288 7 ±0.5 70 1076 75% or 25% ±10% 72 7 ±1 70 269 75% or 25% ±15% 32 7 ±1.5 70 120 Response Rate 75% or 25% ±20% 18 7 ±2 70 67 10% ±3% 384 7 ±0.5 50 768 10% ±5% 138 7 ±1 50 192 10% ±8% 54 7 ±1.5 50 85 10% ±10% 35 7 ±2 50 48 20% ±3% 683 4 ±0.4 40 960 20% ±5% 246 4 ±0.8 40 240 20% ±8% 96 4 ±1 40 154 20% ±10% 61 4 ±1.5 40 68 30% ±3% 896 4 ±0.4 16 384 30% ±5% 323 4 ±0.8 16 96 30% ±8% 126 4 ±1 16 61 Non-response to a Question 30% ±10% 81 Household or Person Trip Rate 4 ±1.5 16 27

26 Standardized Procedures for Personal Travel Surveys 8. A research agency may not release research findings prior to the public release of the findings by the organization that commissioned the study, unless approval of the client organization is obtained to do so; and 9. A research agency must ensure the reasonable safety of its fieldworkers during the execu- tion of a survey. 2.4.2 E-3: Mailing Materials Most surveys involve some activity of mailing materials to respondents, whether this is just an initial contact letter telling about the survey to be done, the sending of recruitment materials, or the full survey form. There is evidence to suggest that the materials used to mail to households, as well as materials for households to mail back, have an effect on response rates. Further dis- cussion of this issue is provided in Section 7.2 of the Technical Appendix. It is recommended that the following standardized approaches be adopted with regard to for- mat and appearance of mailing materials for travel surveys: 1. The use of a stamped return envelope, ideally with instructions on which materials need to be mailed back, and not the use of reply-paid envelopes; 2. The use of a large white envelope (4″ × 9.5″ or larger), with the address printed directly onto the envelope, rather than the use of address labels; 3. Print a recognizable return address on the envelope and indicate the contents of the envelope— at least the survey name; and 4. Affix postage stamps, especially commemorative stamps, rather than using a franking machine or pre-printed bulk mail. 2.4.3 E-4: Respondent Questions In virtually any travel survey, respondents have concerns regarding the legitimacy of the sur- vey and those conducting it. While some of these concerns may be addressed in a cover letter, the typical survey has more nuances than may be explained in a single- (or even double-) page letter. The state of the practice has evolved three methods for respondents to verify the survey, and obtain answers to frequently asked questions. These include the use of 1. Telephone contact numbers; 2. Informational brochures, with frequently asked questions (FAQs); and 3. Internet websites. The use of each of these methods to answer respondent questions and the potential to develop standardized procedures for using these methods are discussed in Section 7.3 of the Technical Appendix. As a standardized procedure for respondent questions, it is recommended that the execution of a travel survey include • A telephone contact within the sponsoring agency; • A toll-free telephone contact within the data collection entity (if different from sponsoring agency); and • Detailed instructions in the form of an informational brochure or fact sheet; care should be taken to ensure that the information is presented in an easy to read manner, with appro- priate use of graphics where possible. Where possible, a website with information about the survey, links to sponsoring agencies, answers to FAQs, email and telephone contact for assistance or further information, and the abil- ity to download survey materials should be provided.

Summary of Recommended Standardized Procedures and Guidelines 27 If non-respondents to household interview surveys tend to travel more than respondents, then providing an additional alternative that permits responding when convenient to the respondent may increase the response rate. Accordingly, providing respondents with online response capabilities is encouraged. 2.4.4 E-5: Caller ID “Caller ID,” “Caller Line Identification,” and “Caller Display” are different names for the ser- vice provided by many telephone companies that allows the customer to see the telephone num- ber, and sometimes the directory listing, of the person who is calling. With the addition of Call Blocking, telephone customers may automatically block incoming telephone calls that do not permit the display of a telephone number. In light of the general decline in telephone survey response rates, it is incumbent upon legit- imate survey researchers to provide any information that may encourage responses from the full range of households. One of the primary uses of Caller ID is for households to screen out unwanted telephone calls by simply ignoring calls that do not display a known number or identity of the caller. Further information on this is provided in Section 7.4 of the Technical Appendix. It is recommended as a standardized procedure that Caller ID be provided by the entity con- ducting the telephone calls—whether a contracted survey firm, university, or government agency—because existing data indicate that providing any ID at all may assist response rates more than being unrecognized. However, after careful review, it is concluded that there are no standardized procedures that can be recommended regarding Caller ID listings. 2.4.5 E-9: Answering Machines and Repeated Call-Back Requests There are two related issues encountered by every telephone-based survey: first, when an answering machine is reached, does it assist completion rates if a message is left? Second, when a household requests an interviewer call them back at another time, is there a point beyond which repeated call backs do not increase completion rates? Each of these issues is discussed in Section 7.5 of the Technical Appendix. It is recommended that a standardized procedure be adopted that messages be left on answer- ing machines, as follows: 1. When an answering machine is reached on the initial recruitment/screening call, a mes- sage should be left at least once in the call rotation before classifying the number as non- responding. The message should identify the client organization and the nature of the sur- vey and provide a toll-free number for the household to contact should they desire to participate. The message should be short (no more than 15 seconds) and preferably pro- vided by a “live” interviewer as opposed to a recorded message. 2. When an answering machine is reached on a reminder telephone call, a message should always be left. 3. When an answering machine is reached during telephone retrieval of travel information, a message should always be left. It is also recommended that telephone survey protocols include a process for complying with call back requests, whether they occur in the recruitment or retrieval portion of a tele- phone survey. After the fifth request for a call back from the same household, the household should be categorized as a “soft” refusal and therefore eligible for any “soft refusal” conver- sion techniques in use.

2.4.6 E-10: Incorrect Reporting of Non-Mobility In any travel survey, it is to be expected that some portion of respondents will not have trav- eled from their home during the survey period. However, a claim of non-mobility on the diary day or days also may be a form of non-response. Some potential respondents may realize that a claim of non-mobility will shorten significantly the length of the interview. The issue addressed in this section, and elaborated in Section 7.6 of the Technical Appendix, is to reduce the incor- rect reporting of non-mobility that is made as a form of non-response. Standardized procedures are recommended in three portions of the travel survey process: data collection, data recording, and reporting. In Data Collection It is recommended that a question to verify reported non-mobility be asked of all persons who report they did not travel (stayed in one place/did not leave home) during the entire travel period. The question wording in the 2001 National Household Travel Survey (NHTS) (“Does this mean {you/subject} stayed at {the same place/home} all day?”) should suffice. To explore the issue of non-mobility further, it is recommended to include questions that gently challenge persons who report non-mobility by asking for the reason(s) why no travel was made during that day. In Data Coding At a minimum, it is recommended that the data set include an indicator to distinguish between cases where a person indicated that he or she did not travel and those where a person refused to provide travel data. In Reporting It is recommended that the survey results report include the percent of non-mobile person days. In single day surveys, this would be determined by the number of persons reporting that they did not travel, divided by the total number of persons reporting. If questions are asked regarding the reasons why no travel was asked, as advanced practice, the report should include analyses of these reasons and the characteristics of persons who reported no travel. 2.4.7 E-11: Recording Time of Day This item refers to standards for coding time-of-day values for database entry and relates to how data are recorded (i.e., entered by the interviewer) and stored, rather than how respondents provide the information. Further discussion is provided in Section 7.7 of the Technical Appen- dix. It is recommended that time of day for data entry and storage be undertaken using two fields: one for the day number, and one for the time in military time (00:00–23:59). 2.4.8 E-12: Time of Day to Begin and End Reporting Surveys use various different times at which to start and end the time for a 24-hour (or longer) diary. The aim is usually to choose a time that is expected to interrupt relatively little travel so that respondents will not be put in the awkward situation of trying to respond about travel that had started before the start time of the diary. However, there is wide discrepancy in the selection of this time, which appears to range anywhere from midnight to 5 A.M. The research for this item is described in Section 7.8 of the Technical Appendix. It is recommended that start and end times for 24-hour diaries should be 03:00 A.M. to 02:59 A.M. In the case of diaries that cover more than 1 day, end times are extended by 24 hours for each additional day. 28 Standardized Procedures for Personal Travel Surveys

Summary of Recommended Standardized Procedures and Guidelines 29 2.4.9 E-13: Creation of ID Numbers Each completed survey requires a unique identification number. In addition, if data are retained on incomplete households, then all contacted households require a unique identifica- tion number. The primary issue with respect to identification numbers is that the numbers should permit ready retrieval of specific records and should provide a unique identification for each unit in the survey. In addition, there is the potential to provide some additional informa- tion through the identification number, such as the membership in a specific sampling category, thereby permitting easy checking of the sampling progress during the survey and ready identifi- cation for purposes of expansion and weighting after the survey is completed. These ideas are explored in detail in Section 7.9 of the Technical Appendix. It is recommended that 1. An ID number should be assigned at the outset to each eligible address or telephone num- ber in the contact list and this number should remain attached to the person or household for the duration of the survey. Telephone numbers or addresses that are established to be non-household numbers should not be assigned an ID number. 2. A stratification-based ID number should be used for all stratified samples, while date-based ID numbering should be used for surveys where sampling is performed by simple random sampling or systematic sampling. 2.5 Data Coding Including Geocoding 2.5.1 C-1: Geocoding Standards Geocoding is the process of identifying the geographic location of a trip end and coding a number—e.g., a traffic analysis zone (TAZ), census tract or block, or latitude and longitude— to represent that location. This item is concerned with developing standards for the methods used to geocode travel data in household travel surveys. It is discussed at length in Section 8.1 of the Technical Appendix. It is recommended that • All travel surveys should geocode trip ends to latitude/longitude. • U.S. State Plane and other North American Datum coordinate systems (e.g., NAD27, NAD83) be used in geocoding unless there is a specific need to use another format. • TIGER/Line files be used as reference databases for address matching. • Information about frequently visited locations be collected and geocoded in the recruit- ment stages of a survey to maximize the opportunity to re-contact households to check addresses that cannot be matched. • Geocoding for non-household and non-habitually visited locations be performed within a few days of data retrieval, also to allow households to be re-contacted if necessary. • Respondents be asked for the names of cross streets and/or landmarks during data retrieval. • Interviewers should have a good knowledge of the survey area or have access to gazetteers containing accurate addresses for shopping centers and schools. Online address directories (e.g., www.infoseek.com, www.usps.com) should be used to locate addresses in situations where supplementary information is not available. • Pre-tests and evaluations should always be performed to assess the success of geocoding using one or all of the following methods: – Aggregation checks on the location of geocodes; – Checking addresses against other information such as telephone exchanges;

30 Standardized Procedures for Personal Travel Surveys – Verifying that one trip starts where the other finishes; and – Cross checking reported distances and times with those calculated from geocoded points. 2.5.2 C-2: Level of Geocoding To Be Performed It is theoretically possible to geocode 100% of all trip ends in a survey, but in practice this is difficult, if not impossible. Most travel surveys will encounter some difficulties in geocoding, so there is a need to determine a reasonable minimum match rate that could be achieved in most survey settings. The reader is referred to Section 8.2 of the Technical Appendix for further infor- mation on this topic. It is recommended that standardized procedures be adopted so that 1. Surveys should successfully geocode no less than 99% of household addresses, 95% of school and workplace addresses, and 90% of other locations to latitude/longitude. 2. Any locations that cannot be geocoded to latitude/longitude should be referenced at least to a TAZ to avoid systematic bias. 3. Where it is not possible to match out of region locations with a TAZ, it is proposed they be assigned to a representative point outside the study area. 2.5.3 C-4: Missing Values, Use of Zero, Etc. There is considerable variability in how missing data are recorded in transport surveys and even variability within the same survey. The issues in this item, which are discussed in detail in Section 8.3 of the Technical Appendix, relate to standardizing the ways in which missing data are flagged and how zeroes and blanks are to be used in coding. It is recommended that the following standardized procedures be adopted together as a group because adoption of some without others will actually increase ambiguities in the data: 1. No blanks: Blanks should never be a legitimate code, and all data fields must contain alphanumeric data. 2. Missing data: Missing data—whether as the result of a respondent refusal, an indication that the respondent does not know the answer, or a legitimate skip of the question—should receive a coded numeric value. These values should be negative values (because negative values will not normally occur in a data set) and should be −99 for a refusal. For “don’t know” responses, it should be set as −98. For legitimate skips or non-applicability of a ques- tion, the value −97 should be entered. 3. Correspondence between numeric values and codes: In any question where a legitimate response could be zero, the code for that response will be the number zero (0). This will normally apply to any question requesting a count of elements, where a count of zero is possible—e.g., number of workers in the household, number of children in the household, number of infants in the household, number of cars available to the household, etc. In like manner, the count that is the response will be the coded value in all cases. 4. Coding the number of person trips reported: In all personal travel surveys that seek to ascertain trip-making behavior of individuals, the person record should contain a count of the number of trips reported by the individual. A count of 0 is to be used only to indicate the response that the person did not travel on the diary day. If no travel information was provided, then the value coded should be −99. 5. Coding binary variables: The principal binary variables in personal travel surveys are yes/no responses and responses to gender. For questions to which the response is either “yes” or “no,” the response of “yes” is coded as 1 and the response of “no” is coded as 2. For response to the gender question, “male” is 1 and “female” is 2.

Summary of Recommended Standardized Procedures and Guidelines 31 2.5.4 C-5: Coding Complex Variables This item is concerned with how to code the responses to certain types of questions involving categories that may vary from survey to survey, depending on the level of detail required for a specific survey. Among the questions that fit within this item are income and activity. There are a number of complex variables where it would be useful to adopt a consistent pro- cedure for the values used to report the data. This would enhance comparability of surveys and remove potential ambiguities. It is also contingent on standardizing response categories to cer- tain questions, as discussed in Section 2.1.2. These proposed procedures should be developed not only for any appropriate questions in the minimum question specifications, but also for additional questions that may be used in many travel surveys. Further discussion may be found in Section 8.4 of the Technical Appendix. It is recommended that 1. Multi-digit codes for complex variables, similar to the codes shown in Table 7, be adopted in all future travel surveys. For income, the codes specified in Table 7 are recommended to be used for consistency across surveys. 2. The activity categories shown in Table 8 be adopted for general use in future travel surveys. These categories are based on more or less commonly used trip-purpose categories, but provide for a much more detailed breakdown into activity types that can be used in activ- ity surveys. Table 7. Possible coding for varying income detail. Minimum Detail for Income Categories Minimum Coding More Detailed Categories Under $5,000 Under $10,000 00 $5,000–$9,999 $10,000 –$14,999 $10,000–$19,999 01 $15,000–$19,999 $20,000–$24,999 $20,000–$29,999 02 $25,000–$29,999 $30,000–$34,999 $30,000–$39,999 03 $35,000–$39,999 $40,000–$44,999 $40,000–$49,999 04 $45,000–$49,999 $50,000–$54,999 $50,000–$59,999 05 $55,000–$59,999 $60,000–$64,999 $60,000–$69,999 06 $65,000–$69,999 $70,000–$74,999 $70,000–$79,999 07 $75,000–$79,999 $80,000–$84,999 $80,000–$89,999 08 $85,000–$89,999 $90,000–$94,999 $90,000–$99,999 09 $95,000–$99,999 $100,000–$104,999 $100,000–$109,999 10 $105,000–$109,999 $110,000–$114,999 $110,000–$119,999 11 $115,000–$119,999 $120,000–$129,999 12 $120,000–$124,999 $125,000–$129,999 $130,000–$134,999 $130,000–$139,999 13 $135,000–$139,999 $140,000–$144,999 $140,000–$149,999 14 $145,000–$149,999 $150,000 and over 15 $150,000 and over Legitimate skip –997 Legitimate skip Don’t know –998 Don’t know Refused –999 Refused More Detailed Coding 000 005 010 015 020 025 030 035 040 045 050 055 060 065 070 075 080 085 090 095 100 105 110 115 120 125 130 135 140 145 150 –997 –998 –999

32 Standardized Procedures for Personal Travel Surveys Primary Category Code Secondary Categories Code Tertiary Categories Sleeping/napping 011 Sleeping Preparing a meal/snack Eating a meal/snack Preparing/eating meals/snack/drinks 012 Other specified food-related activities Indoor cleaning Outdoor cleaning Gardening/ tending plants Care of textiles and footwear Home maintenance/cleaning 013 Other specified home maintenance and cleaning Paying household bills Budgeting, organizing, planning Selling, disposing of household assets Household management 014 Other specified household management Showering, bathing, personal grooming Health/medical care to oneself Receiving personal care from others Personal care activities 015 Other specified personal care activities Using telephone (fixed line) (not incl. telephone shopping) Using cell phone (not incl. telephone shopping) Sending/reading/receiving email Internet browsing (not incl. online shopping) Shopping for goods and services using telephone (fixed line) Shopping for goods and services using cell phone Shopping for goods and services using Internet Using computer/telephone 016 Other specified use of computer/telephone Caring for children Teaching, training, helping children Caring for adults Caring for others 017 Other specified caring for others Paid work – main job Paid work – other job Paid work 018 Other specified at home paid work Home 01 Other specified at home activities 019 Not further defined (n.f.d.) Regular hours Overtime hours Extra hours (not paid as overtime) Work 02 Main job 021 Other specified main job activities Regular hours Overtime hours Extra hours (not paid as overtime) Other job 022 Other specified job activities Regular hours Overtime hours Extra hours (not paid as overtime) Work in internship, apprenticeship, etc. 023 Other specified internship/apprenticeship activities Unpaid work in family business 024 n.f.d. Breaks and interruptions from work 025 n.f.d. Training and studies in relation to work 026 n.f.d. Volunteer work and community services 027 n.f.d. Looking for work Looking for work/setting up business 028 Looking for/setting up business Other specified work- related activities 029 n.f.d. Code 0110 0121 0122 0129 0131 0132 0134 0138 0139 0141 0142 0143 0149 0151 0152 0153 0159 0161 0162 0163 0164 0165 0166 0167 0169 0171 0172 0173 0179 0181 0182 0189 0190 0211 0212 0213 0219 0221 0222 0223 0229 0231 0232 0233 0239 0240 0250 0260 0270 0281 0282 0290 Table 8. Guidelines for trip-purpose/activity categories.

Summary of Recommended Standardized Procedures and Guidelines 33 Primary Category Code Secondary Categories Code Tertiary Categories Attendance at childcare 031 n.f.d. Attendance at school 032 n.f.d. Attendance at college 033 n.f.d. Breaks/waiting at place of general education 034 n.f.d. Self study for distance education course work 035 n.f.d. Homework, study, research 036 n.f.d. Career/professional development training and studies 037 n.f.d. Education/ Childcare Activities 03 Other specified activities relating to education/childcare 039 n.f.d. Restaurant Restaurant/café 041 Café/snack bar/cafeteria Take out Fast food 042 Eat in At friends’ home 043 n.f.d. Picnicking 044 n.f.d. Eating Out 04 Other specified eating out 049 n.f.d. Post Office Availing of/shopping for administrative services 051 Other specified administrative service Availing of/shopping for educational services 052 n.f.d. Banking/credit union Insurance Real Estate Tax or accountant Legal services Personal Business 05 Availing of/shopping for professional services 053 Other specified professional services Availing of/shopping for government/public services 054 n.f.d. Hairdresser/barber/beautician Availing of/shopping for personal services 055 Other specified personal service Medical Dental Eye care Physiotherapy Availing of/shopping for medical and health care services 056 Other specified healthcare service Availing of/shopping for rental services 057 n.f.d. Availing of/shopping for repair and maintenance services 058 n.f.d. Other specified activities relating to personal business 059 n.f.d. Purchasing food and household supplies (groceries) 061 n.f.d. Purchasing clothes, shoes, personal items 062 n.f.d. Purchasing school supplies 063 n.f.d. Purchasing medical supplies 064 n.f.d. Purchasing household appliances, articles, equipment 065 n.f.d. Purchasing capital goods (cars, houses, etc.) 066 n.f.d. Shopping 06 Comparison shopping 067 n.f.d. Window shopping 068 n.f.d. Purchasing other specified goods. 069 n.f.d. Code 0310 0320 0330 0340 0350 0360 0370 0390 0411 0412 0421 0422 0430 0440 0490 0511 0519 0520 0531 0532 0533 0534 0535 0539 0540 0551 0559 0561 0562 0563 0564 0569 0570 0580 0590 0610 0620 0630 0640 0650 0660 0670 0680 0690 Table 8. (Continued). (continued on next page)

34 Standardized Procedures for Personal Travel Surveys Primary Category Code Secondary Categories Code Tertiary Categories Communication/ correspondence 071 n.f.d. Doing activities/going to places and events together Receiving visitors Visiting friends and relatives Socializing activities 072 Other specified socializing activities Participating in community celebration of historical/cultural events Participation in non-religious community rites of weddings, funerals, births, etc. Participating in community social functions Participating in religious activities Participating in religious/community/ cultural events/activities 073 Participating in other specified religious/community/cultural activities Attendance at movies/cinema Attendance at concerts Attendance at sporting events Social and Recreational Activities 07 Visiting entertainment and cultural venues 074 Attendance at library Attendance at amusement park Attendance at museum/exhibition/art gallery Attendance at zoo/animal park Attendance at other specified entertainment and cultural venues Organized sport Informal sport Exercise (excludes walking) Walking, hiking, bushwalking Fishing, hunting Driving for pleasure Indoor and outdoor sporting activities 075 Participation in other specified indoor and outdoor sporting activities Card, paper, board games, crosswords Gambling Arcade games Home computer games Hobbies, handwork, crafts Games/hobbies/arts/crafts 076 Other specified activities relating to games/hobbies/arts/crafts Reading Watching/listening to television/video programs/radio Print/audio/visual media 077 Other specified activities using print, audio or visual media Other specified social and recreational activities 079 n.f.d. Accompanying children to receive personal services Accompanying children to receive medical/health services Accompanying children to school, daycare centers Accompanying children to sports lessons, etc. Accompanying children to places 081 Accompanying children to other specified places Accompanying adults to receive personal services Accompanying adults to receive medical/health services Accompanying adults for shopping Accompanying adults for social activities Accompanying adults to cultural, sports and entertainment venues Accompanying adults to places 082 Accompanying adults to other specified places Code 0710 0721 0722 0723 0729 0731 0732 0733 0734 0739 0741 0742 0743 0744 0745 0746 0747 0749 0751 0752 0753 0754 0755 0756 0759 0761 0762 0763 0764 0765 0769 0771 0774 0779 0790 0811 0812 0813 0814 0819 0821 0822 0823 0824 0825 0829 Accompan- ying/ helping others and travel- related 08 Table 8. (Continued).

Summary of Recommended Standardized Procedures and Guidelines 35 Table 3 used in Section 2.1.2 also provides categories for a number of questions which are con- sistent with the coding procedure proposed here. It is recommended that the codes in that table also be adopted as a consistent set of codes for the variables listed therein. 2.6 Data Analysis and Expansion 2.6.1 A-1: Assessing Sample Bias Sample bias is a systematic error in sample survey data. It reflects a consistent deviation of sample values from true values in the population. Bias can occur within individual observations when, for example, a faulty measurement device is used and a consistent error is introduced into each observation. Of course, bias in individual observations is carried through to aggregate val- ues of the sample such as means and proportions. However, even if individual observations are not biased, if the sample is not representative of the population, assumptions that it is produces biased estimates of the population. This is a condition that can occur quite readily because draw- ing a truly random sample from the population is complicated by factors such as the practical difficulty of establishing a perfect sampling frame, having an equal likelihood of contacting each sampling unit, and obtaining full response from each sampling unit. The issues of sample bias and its assessment are discussed in detail in Section 9.1 of the Technical Appendix. It is recommended that the following standardized procedures be adopted with respect to bias in travel surveys: 1. Each travel survey should test for bias. 2. The following variables should be used to test for bias: – Household size; – Vehicle availability; – Household income (if collected); – Race of each person in the household; – Age of each person in the household; and – Gender of each person in the household. 3. The variables should be measured as follows: – Household size: mean value; – Vehicle availability: categories of 0, 1, 2, and 3+; Primary Category Code Secondary Categories Code Tertiary Categories Pick up someone or get picked up Pick up or drop off other people/get picked up or dropped off (private car, car/van pool, shuttle/limousine) 083 Drop off someone or get dropped off Activities related to bus, public transit, and group rides (except car/van pool and shuttle/limousine) 084 Wait for/get on vehicle Leave/get off vehicle Change travel mode 085 n.f.d. Other specified activity related to accompanying others or travel-related 089 n.f.d. No activity 091 n.f.d. No recorded activity 092 n.f.d. No activity 09 No further activity recorded 093 n.f.d. Other 99 n.f.d. 990 n.f.d. Code 0831 0832 0841 0842 0850 0890 0910 0920 0930 9900 Table 8. (Continued).

– Household income: categories corresponding to those in Table 7 in Section 2.5.4; – Race: categories of white, black/African American, American Indian/Alaska native, Asian, Native Hawaiian/Pacific Islander, other single race, and two or more races; – Age: categories of 0–5, 6–10, 11–14, 15–17, 18–64, 65–74, 75 and over; – Gender: male and female. 4. Total error should be measured using the Percentage RMSE statistic defined in Equation 1. where ni = number of variables i; nji = number of categories j in variable i; rij = reference value of variable i in category j; and sij = sample value of variable i in category j. 2.6.2 A-2: Weighting and Expansion of Data Weighting is the process of assigning weights to observations in a sample so that the weighted sample accurately represents the population. Expansion is the multiplication applied to each observation in a sample so that the expanded sample is an estimate of the population. Weight- ing is determined by comparing values of variables within the sample with values of correspond- ing variables from a reliable external source such as the census. Expansion factors are the inverse of the sampling rate. Weighting and expansion are often combined into a single factor or weight, which reflects both the relative representativeness of each observation in the sample and the number of simi- lar cases each observation in the sample represents in the population. Separate weights are usu- ally assigned to households, persons, and trips. These weights sum to the number of households, persons, and trips in the population, respectively. The reader is referred to Section 9.2 of the Technical Appendix for further elaboration. It is recommended that the following standardized procedures be adopted: 1. Each travel survey should conduct a weighting and expansion exercise to include the weights in the data set and to include a description of the weighting process in the metadata; 2. The weights should include expansion factors so that the sum of the weights match popu- lation estimates; and 3. The two-stage procedure, described in the technical appendix, Section 9.2.2, should be adopted as the standard method of calculating weights. 2.6.3 A-3: Missing Data Imputation As discussed in Section 9.3 of the Technical Appendix, imputation is the substitution of val- ues for missing data items or for values of data items that are known to be faulty. Data values are known to be faulty if they are infeasible (e.g., a 5-year old with a driver’s license) or are incon- sistent with other information known of an individual or their household. There are two mech- anisms for substituting values for missing or faulty data items—deductive imputation (or infer- ence) and regular imputation. Inference involves deriving the value of a missing or faulty data item from the information known of a respondent or their household, when such a derivation can be made with relative certainty. For example, the gender of a person can often be inferred from their first name, and a person 16 years of age or older who reports making multiple trips alone by car probably has a driver’s license. Imputation, on the other hand, is the generation of Percent RMSE n n r s ri ji ij ij ijj nji i n = −⎛ ⎝⎜ ⎞ ⎠⎟∑ 1 1i∑ × 2 100 1( ) 36 Standardized Procedures for Personal Travel Surveys

Summary of Recommended Standardized Procedures and Guidelines 37 a likely value for missing data with no assurance that the imputed value is correct on a case-by- case basis. For example, if the number of vehicles owned by a household is missing, a likely num- ber could be imputed by considering the household income, number of licensed drivers, and age of the members of the household. Imputation is expected to produce the correct distribution of values for each variable even though individual imputed values are not necessarily correct. Imputation is the last resort in replacing missing or faulty data items with valid values. Every effort is first made to limit missing or faulty data through good survey design, well-managed survey execution, and aggressive editing and call-back to respondents. However, when the best efforts to obtain accurate reported information on each item fails, inference—followed by imputation—should be applied. Inference should always precede imputation because inferred values are more accurate than imputed values. It is recommended that the following standardized procedures be adopted with respect to imputation in household travel surveys: 1. Data editing should be conducted in all travel surveys; 2. Inference should always precede imputation; 3. Any imputation procedure with the exception of overall mean imputation may be used; 4. If hot-deck imputation is employed, it should be conducted without replacement; and 5. Every inferred and imputed value should be flagged in the data to clearly indicate its nature. 2.6.4 A-4: Data Archiving Archiving data preserves the data for future use; it is considered a method for maintaining the value of data and allows space to be freed on expensive data storage mediums. Archiving was not conducted in the past because transport agencies did not feel this was part of their responsibil- ity, agencies were reluctant to make their data readily available to the public, and archiving was not accounted for in initial budgets of projects. A key to effective data archiving is the assign- ment of responsibility and adequate funding in the initial stages of project design. The issue of archiving data is discussed at some length in Section 9.4 of the Technical Appendix. It is recommended that the transportation profession adopt the following principles to archive transportation data: 1. The sponsoring agency should be the primary organization responsible for archiving the data, associated metadata, and any relevant archiving auxiliary data. 2. Maps of zones, locations, and networks should be included in the archive. The recognized standard for storing travel behavior data is the ASCII format in order to overcome prob- lems associated with archived spatial data networks due to rapidly changing software. 3. Adequate documentation of the data should be archived. Any changes made to the data should be documented, and codebooks and documentation of sampling and weighting procedures need to be archived with the data. 4. Transportation documentation, preservation metadata, and archives should utilize the document type definition (DTD) such as extended markup language (XML). 5. Raw data should be archived. Modified data sets do not need to be stored as long as statis- tical tests and modifications made to the data are thoroughly documented. 6. Telephone recruitment and telephone or mail-back data retrieval and call history files describing call dispositions of sampled households during the recruitment process should also be archived. 2.6.5 A-6: Documentation This section, and Section 9.5 of the Technical Appendix, deals with how to document a house- hold travel survey. Currently, very little has been written about documentation of travel data. The

term “metadata” in European literature is what is generally referred to in U.S. transportation lit- erature as “data documentation.” There has been some writing on metadata in recent literature, but there are no standardized procedures for documentation of household travel surveys. The following is a comprehensive list of the ideal requirements for travel survey documenta- tion and is recommended for adoption as a consistent procedure for household travel survey documentation: 1. Sponsorship for the survey—name of the agency, ministry, or organization sponsoring the travel survey and, if the data were collected by an external research organization, the name of fieldwork agency. 2. Survey purpose and objectives—description of why the survey is being conducted, what it hopes to achieve, and expected results. 3. Questionnaire and other survey documents—wording of all questions including specific interviewer and respondent instructions. It also includes aids such as recruitment scripts, interview script (telephone and personal interview), maps, travel diaries, memory joggers, etc. These should be provided as an appendix. 4. Other survey materials—interviewer instruction manuals, validation of results (techniques employed), codebooks, incentive descriptions (pre or post; type of incentive; if monetary, the level offered). 5. Population and sampling frame—a description of the population that the survey is intended to represent as well as why this population was selected and a description of the sampling frame used to identify this population. 6. Sample design—a complete description of the sample design: sample size, sampling frame, information on eligibility criteria, and screening procedures. 7. Sample selection procedures—methods by which respondents were selected by the researcher, details of how the sample was drawn, the levels of proxy reporting tolerated, what constituted a complete household, and the sample size. 8. Sample disposition—refusals, terminations, ineligibles, completed interviews, and non- contacts. Also a description of the level of item non-response accepted for key variables and why. 9. Response rates—how the eligibility rate for the unknown sample units was determined, a description of the response rate formula used, and the calculation of the overall response rate for a two or more stage survey. 10. Processing description—editing, data adjustment, and imputing procedures used. 11. Precision of estimates—sampling error, including other possible sources of error to inform user of accuracy or precision, and a description of weighting or estimating procedures. 12. Basic statistics—a description of all base percentages or estimates on which conclusions are made. 13. Data-collection methods—survey mode and procedures. 14. Survey period—dates of interviews of fieldwork or data collection and reference dates for reporting—e.g., time, day, and date when calls or other forms of contact were made. 15. Interviewer characteristics—number and background of fieldwork staff. 16. Quality indicators—results of internal validity checks and any other relevant information such as external research. 17. Contextual information—any other information required to make a reasonable assess- ment of the findings and data. 18. Conduct of geocoding—a description of how geocoding was conducted, including the level of data imputation and inference and how these values are flagged, etc. It is also important for the documentation to incorporate organizational documentation. This includes the request for proposals and proposal submission, contracts and modifications, all progress reports, key meetings results, costs, key personnel, and information about situations 38 Standardized Procedures for Personal Travel Surveys

Summary of Recommended Standardized Procedures and Guidelines 39 that occurred during the period of the survey. This may include both positive and negative infor- mation, with respect to the overall survey process. Preserving this information will allow agen- cies to improve on future research projects and proposal submissions because staff writing such documents may consult older examples of these types of documents (Sharp, 2003). 2.7 Assessment of Survey Quality 2.7.1 Q-1: Computing Response Rates Proper calculation of response rates is important because response rates are used by analysts to assess survey quality. Higher response rates are usually desired to reduce the likely incidence of non-response bias. Until recently, CASRO was the only organization with its own method for calculating response rates. However, some years after the development of the CASRO method, the American Association of Public Opinion Research (AAPOR) developed another method for calculating response rates. Both the CASRO and AAPOR formulas are commonly used by sur- vey practitioners. These response rate calculations and related issues are discussed in Section 10.1 of the Technical Appendix. Standardized procedures are proposed regarding the definitions of the components used in the calculation of response rates. Final disposition codes should be divided into four major groups, regardless of the survey modes to be used: 1. Complete interviews; 2. Eligible cases that were not interviewed (non-respondents); 3. Cases of unknown eligibility; and 4. Ineligible cases. These categories can be sub-classified further, depending on the level required by the survey firm and the survey execution method employed. Final disposition codes, adapted from the AAPOR standards, suggested for consistency among transportation surveys, are shown in Table 9. We recommend that the AAPOR (RR3A) formula be adopted for the calculation of response rates for all household and personal travel surveys (Equation 2): where SR = number of complete interviews/questionnaires, PI = number of partial interviews/questionnaires, RB = number of refusals and terminations, O = other, NC = number of non-contacts, UH = unknown if household occupied, UO = unknown other, and eA = estimated proportion of cases of unknown eligibility that are eligible (AAPOR eligibil- ity rate: the same formula for calculating the eligibility rate is used). The eligibility rate for the unknown sample units will vary from survey to survey. It is recom- mended that careful consideration is given to disposition codes, that the bounds of the research are clearly defined, and that the eligibility rate for the unknown sample units should be defined from this analysis. In transport surveys (as recommended as a standard by AAPOR), it is recommended that 1. The estimation of the eligibility rate be left to the discretion of the organization(s) and indi- vidual(s) undertaking the research; RR A SR SR PI RB O e UH UO NCA 3 2= +( )+ +( )+ + +( ) ( )

40 Standardized Procedures for Personal Travel Surveys 2. The estimate for eligibility from unknown cases should be based on the best available sci- entific information; and 3. The basis of the estimate should be stated explicitly and explained. It is recommended not to use the terms resolved and known, and unresolved and unknown, inter- changeably. Depending on the bounds of the study conducted, cases labeled as eligible may not be resolved. This arises when call backs are given eligible status. Clearly, however, these calls have not been resolved; therefore, using the terms interchangeably in this situation would be incorrect. 2.7.2 Q-2: Transportation Measures of Quality A variety of data quality measures have been proposed in this study but, in this section, we consider variables that have not been used elsewhere. The types of variables considered are those that are temporally and spatially stable and, therefore, should acquire similar values among sur- veys. Special circumstances may cause values to deviate from the norm but, generally, deviations from standard values are an indication that the data are not of the expected quality. As documented in Section 10.2 of the Technical Appendix, past studies suggest that typical non-mobile rates are 20% at the person level and 1% at the household level. It is recommended that these values serve as reference values against which new surveys are measured. Person non-mobile rates less than 20% and household non-mobile rates of less than 1% suggest data Eligibility Eligibility Code Disposition Disposition Code Complete 1.1 Eligible Interview 1.0 Partial 1.2 Refusal and termination 2.10 Refusal 2.11 Household-level refusal 2.111 Termination 2.12 Respondent never available after call back request 2.21 Telephone answering device (message confirms residential household) 2.22 Eligible Non- Interview 2.0 Miscellaneous 2.35 Unknown if housing unit 3.10 Not attempted or worked 3.11 Always busy 3.12 No answer 3.13 Telephone answering device (don’t know if housing unit) 3.14 Telecommunication technological barriers, e.g., call blocking 3.15 Unknown Eligibility, Non- Interview 3.0 Technical phone problems 3.16 Housing unit, unknown if eligible respondent 3.20 No screener completed 3.21 Other 3.90 Out of sample 4.10 Fax/data line 4.20 Non-working number 4.31 Disconnected number 4.32 Temporarily out of service 4.33 Special technological circumstances 4.40 Number changed 4.41 Cell phone 4.42 Cell forwarding 4.43 Business, government office, other organization 4.51 Institution 4.52 Group quarters1 4.53 No eligible respondent 4.70 Not Eligible 4.0 Quota filled 4.80 1 If specified as ineligible in the survey design. Table 9. Final disposition codes for RDD telephone surveys (adapted from AAPOR, 2004).

Summary of Recommended Standardized Procedures and Guidelines 41 quality that is better than average although no clear interpretation of data quality vis-à-vis the non-mobile rate is available at this time. Similarly, person non-mobile rates in excess of 20%, and household non-mobile rates in excess of 1%, indicate below average data quality. Because of the lack of standardization of activity classification and the variety of activity classifi- cation schemes used in transportation at this stage, it is not recommended that activity rates be used to measure data quality. If future travel surveys adopt consistent definitions of activities, as proposed elsewhere in this document, activity rates could be reconsidered as an indicator of data quality. Trip rates from numerous studies show reasonable stability among studies. As expected, trip rates at the person level demonstrate less variability than trip rates at the household level due to the influence of household size. However, household trip rates are frequently quoted and have formed the basis of validation checks in the past. Therefore, it is recommended that the trip rates in Table 10, which include household trip rates, serve as reference values for future travel sur- veys. Deviations from these values must be interpreted by the analyst because the specific rela- tionship between trip rates and data quality has not been established. Note that the trip rates shown in Table 10 are linked, unweighted, person trips per day. 2.7.3 Q-3: Coverage Error Coverage error in surveys is the error incurred by having a sampling frame that deviates from the survey population. It is usually considered to represent the failure to include all the units of the target population. However, in addition to the “under-coverage” that results from exclusion of valid units in the sampling frame, it is also the unintentional inclusion of units in the survey sample (including duplication of units) that do not belong there. This “over-coverage” can occur, for example, when telephone numbers are used as a sampling frame in an RDD sampling process and, as a consequence, households with multiple telephone lines are sampled at a higher rate than those with a single line. Similarly, “under-coverage” can occur in the same type of sur- vey because some households do not own a telephone or have interrupted telephone service. Coverage error is distinct from non-response error although both result from not obtaining information from units in the survey population. Coverage error results from not having some units in the sampling frame or from having units in the sampling frame that do not belong there. Non-response is failing to obtain a response from units that are within the sampling frame. Fur- ther discussion is to be found in Section 10.3 of the Technical Appendix. It is recommended that 1. Coverage error should be estimated in each future travel survey, using Equation 3: where: CE = coverage error in percent; Fx = sample population multiplied by the inverse of the sampling rate; and X ~ = population estimate from an external (reliable) source. CE F X x = − ⎛⎝⎜ ⎞⎠⎟1 100 3% ( ) Trip rate Purpose Mean Value Range All 9.2 8 – 11 HBW 1.7 - HBO 4.7 - Household NHB 2.8 - Person All 3.4 - Table 10. Recommended reference trip rates for travel surveys.

42 Standardized Procedures for Personal Travel Surveys 2. Coverage error should be estimated as the percentage deviation of the population of the study area estimated using the planned sample, from that of the population of the same area using a reliable external source. That is, coverage error must be estimated using the definition of coverage error in Equation 3 above. 3. Each future survey should include descriptions of the survey population and the sampling frame, and coverage error should be reported. 2.7.4 Q-5: Proxy Reporting as a Quality Indicator Proxy reporting in a travel survey is the reporting of one person on behalf of another, as dis- cussed in Section 2.2.2 of this report. While proxy reporting is unavoidable in some cases, it is also susceptible to survey design and the method of survey execution. Because proxy reporting affects the accuracy of the data, it is reasonable to suggest that more proxy reporting is likely to lead to less accuracy in the data. Accuracy is an important compo- nent of data quality and, therefore, it is suggested that the incidence of proxy reporting can be used as a measure of data quality of the data set. This is addressed in more detail in Section 10.4 of the Technical Appendix. It is recommended as a standardized procedure that 1. Each travel survey should include questions on the age of each person in the household (see also Section 2.1.1) as well as the capability of each member over the age of 14 to complete the survey. 2. Only those individuals 15 years of age or older and those capable of completing the survey should be included in estimating the level of proxy reporting in the data. 3. For each individual in the household, it should be established whether the information being reported for that individual was – Prepared by the individual and – Reported by the individual. 4. Each travel survey should report the percentage of proxy reports in the data based on the above conditions relating to what represents a proxy report for this purpose. 2.7.5 Q-6: Validation Statistics Validation is the process of verifying the authenticity of collected data by recontacting a sam- ple of households. It is used in interview-based surveys to determine whether the interviewer actually conducted the interview and whether the information obtained is accurate. It can also be used in self-administered questionnaires where the validation survey then usually involves a face-to-face or telephone interview to check the quality and completeness of data. Validation surveys typically involve a limited set of key questions only. These usually include identifying and trying to make contact with the person involved in the original sur- vey and verifying a few trips reported by the respondent. Validation surveys are conducted to ensure the authenticity and integrity of the data. Further discussion is provided in Section 10.5 of the Technical Appendix. The following recommendations are proposed with respect to validation surveys: 1. Each travel survey should conduct a validation survey. 2. The validation survey should use the following three questions: – Question 1: Did you complete the initial survey? (yes or no)  If “yes,” go to Question 3 below.  If “no,” go to the second question below.

Summary of Recommended Standardized Procedures and Guidelines 43 – Question 2: Did someone else in your household complete the survey? (yes or no)  If “yes,” go to Question 3 below.  If “no,” terminate the validation survey. – Question 3: Select a trip that the respondent is likely to remember from among the trips reported in the initial survey and note the time spent at the destination. Ask the re- spondent to recall the trip in question and to report the approximate time spent at the destination. 3. A statistic should be prepared indicating the percent of validated surveys that provided a negative answer to each of the first two questions or a mismatch on the third question. 4. The commissioning agency should establish at the outset what is considered to be a toler- able level of failure on validation. Acceptance of a 1% failure on the first two questions and 5% on the third might be consid- ered to represent a reasonably good quality. 2.7.6 Q-7: Data Cleaning Statistics Data cleaning or data checking is an activity that is conducted almost routinely in travel sur- veys. It involves checking and, where possible, correcting data values that can be identified as being incorrect. It is usually performed as soon as possible after the data are retrieved. This is to enable queries to be made while the information is still fresh in the memories of the respondents. For errors that are caused or accentuated by the survey process, it also allows timely correction. This is elaborated on in Section 10.6 of the Technical Appendix. The following data cleaning statistic (DCS) provides a mechanism to measure the incidence of cleaned data items in a data set: where: xi,n = ith data item of respondent n count(xi,n) = N = number of respondents in survey I = number of minimum (core) questions It is recommended that all transportation surveys compute and report the DCS statistic and that, based on experience with this statistic, future ranges be established to indicate the quality of the data based on the amount of cleaning required. 2.7.7 Q-8: Number of Missing Values The number of missing values in a data set is a measure of how much information was not collected. If expressed as a proportion of the total number of data items in the data set, it serves as a measure of the relative information content of the data. Thus, it could be used as a measure of data quality. It is important to define what a missing data item is and what it is not. As described in Section 2.5.3, recommended coding practice is to distinguish between non-responses that are refusals— those in which a respondent does not know the answer to the question—and those in which a response would not be applicable. Among these categories, only responses where a respondent either refuses or does not know the answer are truly missing values. Further information is to be found in Section 10.7 of the Technical Appendix. 1 if data item of respondent was cleani nth ed otherwise0{ } DCS count x N i n i I n N = ( ) × == ∑∑ , 11 1

44 Standardized Procedures for Personal Travel Surveys It is recommended that 1. The definition of missing data indicated in Section 10.7 of the Technical Appendix be adopted as a standard definition in transportation surveys; 2. The missing value index (MVI), shown below, be computed for all transportation data sets; and 3. Values representing various levels of data quality be established based on experience with the MVI over time. The MVI is defined as where MVI = Missing Value Index, x*i,n = xi,n = I = number of variables, and N = number of respondents in data set. 2.7.8 Q-9: Adherence to Quality Standards and Guidelines One of the ways to improve the quality of data is to have a checklist of actions that must be performed or standards that must be met in each survey. Such a checklist is not currently accepted or used in reporting on household and personal travel surveys. The reader is referred to Section 10.8 of the Technical Appendix for further information. Ten questions have been compiled to assess the quality of the survey process. It is recom- mended that the following questions be answered for each future travel survey: 1. Has the survey agency an active quality control program in operation? 2. Is a senior, independent staff member responsible for quality control in the organization? 3. Have pretests been conducted? 4. Has a pilot survey (or surveys) been conducted? 5. Have validation surveys been conducted? 6. Have data reported by proxy been flagged to indicate they were obtained by proxy reporting? 7. Have data values obtained through imputation been flagged to indicate the nature of their origin? 8. Has the survey report been prepared and submitted to the client? 9. Has a coding manual and other metadata that accompanies the data been prepared and submitted to the client? 10. Have the survey data been adequately archived in a safe, accessible, and well-recognized data storage location? Answers in the affirmative are favorable; if each affirmative is allowed to count one point, then a score out of 10 would indicate the level of adherence to principles of good survey practice. It is recommended that this statistic be produced for all future travel surveys. 1 if a response to variable i is applicable to respondent n if a response is not app0 licable{ } 1 if data item i of respondent n is missing 0 otherwise{ } MVI x x i n i I n N i n i I n N = ∗ == == ∑∑ ∑∑ , , 11 11

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 571: Standardized Procedures for Personal Travel Surveys explores the aspects of personal travel surveys that could be standardized with the goal of improving the quality, consistency, and accuracy of the resulting data. The technical appendix to NCHRP Report 571 was published as NCHRP Web-Only Document 93.

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