National Academies Press: OpenBook

Standardized Procedures for Personal Travel Surveys (2008)

Chapter: Chapter 1 - Introduction and Research Approach

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Suggested Citation:"Chapter 1 - Introduction and Research Approach." 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 1 - Introduction and Research Approach." 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 1 - Introduction and Research Approach." 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 1 - Introduction and Research Approach." 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 1 - Introduction and Research Approach." 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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1.1 Background Personal travel surveys have been conducted for over 40 years, but during that time no attempt has been made to standardize the process or to institute consistent practices of acceptable quality or reliability. Two TRB conferences—“Household Travel Surveys: New Concepts and Research Needs,” in 1995 and “Information Needs to Support State and Local Transportation Decision Mak- ing into the 21st Century” in 1997 (TRB, 1996 and 1997)—and NCHRP Synthesis of Highway Practice 236: Methods for Household Travel Surveys (Stopher and Metcalf, 1996) emphasized the need for improved standardization in survey data collection. The contention is that standardi- zation of the survey process can lead to efficiencies in the planning and execution of surveys, in the assessment of data quality, and in the comparison of data between one metropolitan area and another. Over the past 40 years, many millions of dollars have been spent on collecting household or person-based data for transportation planning. For most metropolitan areas, the largest routine expenditure made from planning budgets is for the conduct of household or person travel surveys. In 1996, it was reported (Stopher and Metcalf, 1996) that the average survey cost was $400,000 for consultant services for the conduct of household travel surveys. Assuming that only half of the about 350 Metropolitan Planning Organizations (MPOs) in the United States conduct travel sur- veys within any decade, this represents a total expenditure of $74 million in a decade, or about $7.4 million per year. In spite of this huge level of activity and expenditure, there is no consistency in the process of executing surveys, nor are there recognized procedures for assessing the quality of the end product. Nevertheless, even larger sums of money are subsequently spent on develop- ing and using travel-demand models based on these data and in investments into major capital projects, implementation of far-reaching policies, and other related decisions. In some cases, the metropolitan regions that commission travel surveys do not have staff with in-depth knowledge and experience in that field. As a result, some MPOs are unable to make informed selections of consultants to perform surveys and are also unable to assess whether a use- ful product was obtained. Subsequent work in using the data for situation descriptions and mod- eling often reveals serious flaws in the data that could have been avoided if there were either a suf- ficient availability of expertise at the MPOs or a set of clearly defined procedures that could be followed by an MPO in guiding the process, selecting consultants, and assessing the work that was done. Some consultants who undertake such work are also unaware of the difficulties involved in data collection and have a lack of knowledge and expertise in various aspects of collection and assessment of the data that are apparent neither to them nor to the MPOs that may select them. They, too, could benefit from a set of standardized procedures and measures that would aid them in determining the type of survey to undertake, the methods to be implemented, and the means to assess whether the survey was being executed satisfactorily. 5 C H A P T E R 1 Introduction and Research Approach

It has long been held by most metropolitan regions that data collected in one region has little relevance to another region. While there is no doubt that there will be local contextual issues that may make transfer of data difficult or inappropriate at times, the major reason for this perception is that each household travel survey is usually sufficiently different in design and execution from any other survey, the result of which is that comparisons from region to region are completely obscured by methodological and implementation differences. If consistent procedures were applied in the collection of such data, many of the apparent differences between regions may well disappear. In addition, there are often slight variations in question phrasing that are sufficient to introduce major barriers to comparing data; appropriate standardization could remove these bar- riers. This could also lead to a greater willingness of regions to borrow data from each other, and thus reduce the overall necessity to expend so much on collection of new data. It would also help the recognition and capture of travel among regions and, of particular importance, enable relating local to national surveys. The issue of standardizing personal travel surveys was investigated in this study. This involved reviewing past practice, conducting analyses on data sets collected in past travel surveys, conduct- ing new travel surveys, identifying individual aspects of personal travel surveys that potentially could be standardized, evaluating these candidate procedures, and then compiling a set of recom- mended standardized procedures. The execution of this process is documented in the following pages. Forty procedures in travel surveys are recommended for standardization in this study. An additional 20 were identified for possible standardization but were either considered to be less important than those selected or beyond the scope of the project. Included in the report is a sam- ple Request for Proposals (RFPs) to assist metropolitan areas in commissioning travel surveys that are consistent with the proposed standardization. 1.2 Study Objectives The objectives of this project are to develop recommended travel survey procedures that would lead to an overall increase in the quality and reliability of transportation surveys performed at household and person levels and would also improve the comparability between surveys. These recommendations will provide guidance on how to select cost effective survey methods, how to implement the survey, how to analyze the results, and how to report measures that allow the assess- ment of the quality of the data. By standardizing the travel survey process, comparability of data from place to place and time to time will be enhanced. The reliability of the data will be increased, and doubts as to the applicability of data should be able to be removed. It is also an objective of this research to identify the costs and tradeoffs for the procedures and assessment measures that are identified in this research and to establish whether specific procedures and assessment measures are cost-effective. There can be negatives to standardization: namely, the stifling of innovation or the creation of stagnation in a field. Over the past 30 years, many changes have occurred in the conduct of per- sonal travel surveys, and what constitutes best practice has clearly evolved during this time. If rigid standards had been applied early in this process, this evolution may well have been prevented from occurring. Indeed, imposition of rigid standards at the current stage of development of travel sur- vey procedures would likely retard further development. On the other hand, survey practice has not evolved all that far during this period of open practice, and there are too many instances where surveys are conducted that repetitively perpetrate the same errors. In addition, travel survey pro- fessionals have often remained ignorant of developments and improvements from other fields of survey practice. Standardization might have prevented certain known pitfalls and errors and raised the average quality level of travel surveys. The research team was cognizant of these two aspects of standardization while developing the recommendations included in this research. 6 Standardized Procedures for Personal Travel Surveys

1.3 Scope The research conducted in this study has focused on the design, execution, and management of personal travel surveys as conducted in the United States. This does not mean that survey practice in other countries was not considered nor that the experience of survey professionals in other coun- tries was not drawn upon, but merely that standardizing personal travel surveys in the United States was the subject of research in this study. The study team included professionals from Germany, Austria, Canada, Australia, and the United States, and survey practice in these countries was con- sidered in developing the recommendations included in this report. The research included the review of past practice, the analysis of survey data, and the execution of special purpose data collection efforts to investigate specific issues. Of the research targeted at U.S. practice, the investigation involved review of more than 50 past surveys, analysis of travel sur- vey data from 12 surveys conducted between 1990 and 2000, execution of a non-response survey, and execution of a survey to measure the impact on response rate and respondent satisfaction of a household having the same interviewer throughout the interview process. As implied by the title of the study, the research conducted in this study was limited to the consideration of personal travel surveys and excluded freight, vehicle, and inventory surveys. All forms of reporting were considered in this study including mail, telephone, face-to-face inter- view, Internet, and instrumented surveys such as the use of global positioning system (GPS) devices in tracking vehicle and person movements. However, Internet and GPS surveys were considered beyond the scope of the study because they are a new and rapidly developing form of data collection that has not matured to the point where standardization or standardized procedures would be appropriate. Similarly, all data considered in this study have been of revealed travel behavior, rather than of stated behavior as typically collected in stated preference surveys. Stated preference surveys were also considered a developing field and not recommended for standardization in this study. A sample RFP serves as a guide in the commissioning of future personal travel surveys. The sam- ple RFP describes the scope of work recommended in a travel survey and the relationship between individual components of the survey process and the standardized procedures and measures rec- ommended in this study. 1.4 Research Approach The approach adopted in this study was to conduct the research in two consecutive phases. In the first phase, potential areas for standardization were identified, the level of effort to research each estimated, and a subset selected for potential work in the second phase. In the second phase, those areas selected for investigation were formulated into standardized procedures or guidelines, depending on the level of specificity thought to be appropriate. It must be stressed that it was not the intention in this study to establish standards. Rather, the goal of the study was to develop rec- ommended standardized procedures or guidelines for consistent practice that agencies could require in the surveys conducted in their areas or that survey practitioners would voluntarily apply. The research in this study was initiated by a literature review on personal travel surveys, as well as a review of relevant research and current practice of state Departments of Transportation (DOTs) and MPOs. Standardized procedures used or promoted by survey research organizations or associations—such as the Council of American Survey Research Organizations (CASRO), the European Society for Opinion and Marketing Research (ESOMAR), and the International Stan- dards Organization (ISO)—were also reviewed. The procedures and assessment measures were identified as candidate procedures for stan- dardization in the study using information from two sources. First, candidate procedures and Introduction and Research Approach 7

measures were identified from the literature and practice review. Second, they were identified by considering the chronological steps in survey planning and execution, similar to that defined by Richardson et al. (1995) and shown in Figure 1. In reviewing each step of the process, the elements that appeared susceptible to standardization were identified based on the literature review, on team members’ experience, and on the potential for standardization to aid or stagnate the design of personal travel surveys. Once identified, the candidate procedures for standardization were evaluated. The criteria used to evaluate them included extent of current use, perceived value, affordability, common definition, uniform method of application, and whether there were interdependencies between the procedure or measure and other procedures or measures. Weights were assigned to the criteria, and each can- didate procedure or measure was scored on the criteria. A total score for each candidate process was established by summing the product of the weight and score on each criterion. These scores were used to prioritize the candidate procedures for review in the remainder of the project. Some survey procedures and assessment measures required no further work before being rec- ommended as a standardized procedure, but most required further analysis to assess their effec- tiveness and applicability. Some procedures and measures were tested using existing data sets, such as the 1995 Nationwide Personal Transportation Survey (NPTS), or recent metropolitan travel sur- veys. Two surveys were specifically conducted to address issues that could not be answered using existing data. The first survey involved testing the impact of having the same interviewer (or at least a limited number of interviewers) deal with the same household throughout the survey. The results were compared with those using regular interviewing procedures where there was no attempt to keep the same interviewer in consecutive contact with the same household. The second survey involved undertaking a non-response survey to determine the probable reasons for refusing to respond or for terminating part way through the survey process. The results were used to suggest strategies that could be used to increase response rates by changing aspects of the design and con- duct of the survey. 8 Standardized Procedures for Personal Travel Surveys Selection of Survey Method Sample Design Pilot Test(s) Survey Fielding Survey Instrument Design Data Coding Pre-Survey Planning Data Editing Data Correction and Expansion Data Analysis Cleaning Up Presentation of Results Figure 1. The transportation survey process (Richardson et al., 1995).

The results of the study have been publicized and disseminated in several ways. First, NCHRP Research Results Digest No. 261: The Case for Standardizing Household Travel Surveys (TRB, 2002) was prepared to summarize the findings of Phase 1 of the project. It was distributed at the 2002 Annual Meeting of the Transportation Research Board and through the normal channels by NCHRP thereafter. The digest includes a list of candidate procedures and measures considered in Phase 2 of the project. Second, an interim report documenting Phase I of the project was completed in June 2001. Third, papers on results emerging from this study have been presented at several con- ferences (Alsnih and Stopher, 2004; Stopher, Wilmot, Stecher, and Alsnih, 2004; Nilufar and Wilmot, 2003; Stopher et al., 2004; Stopher and Wilmot, 2002). Last, the issue of identifying appro- priate procedures for standardization of personal travel surveys was the topic of the first half of the 7th International Conference on Travel Survey Methods held in Costa Rica in August 2004. At the conference, the results of the NCHRP study were related to the delegates in a presentation and resource paper, and individual aspects of the travel survey process were discussed in eight work- shop sessions. It is expected that the information in this report will be useful to transportation practitioners in state DOTs and MPOs in preparing statistically sound data collection and management programs. It is also expected to be useful to travel survey professionals in designing their surveys, training their staff, managing the survey process, reporting the results, and archiving the data. The opportunity to compare results among travel surveys and to assess the potential of transferring data from one location and time period to another will be enhanced with the application of the recommendations in this report. At the same time, these recommendations should not prevent introduction of new procedures to thereby stifle innovation; a balance must be maintained between standardization and new development. Also, allowance should be made to amend or update the recommendations of this report as new and improved information is gained. 1.5 Report Organization This report has been produced in two parts—NCHRP Report 571, the printed report, and NCHRP Web-Only Document 93, the technical appendix. NCHRP Report 571 is organized as follows: • Chapter 1 is an introduction to research and an outline of the report. • Chapter 2 summarizes the recommendations that have been developed. The reader who desires to know why specific recommendations are made or what research and reviews were undertaken should consult Chapters 4–10 in the Technical Appendix. • Chapter 3 outlines recommendations for training and dissemination of the research results. • Chapter 4 provides a description of the areas that are recommended for further research for the development of standardized procedures in personal travel surveys. • Chapter 5 is sample template for RFPs that embodies all of the standardized procedures and guidelines that are summarized in Chapter 2. • Glossary provides terms used in surveys. The reference section contains references cited in this report. Intentionally, these have been kept to a minimum. An exhaustive set of references is to be found in Chapter 11 of the Technical Appen- dix. The Technical Appendix is available on the TRB website as NCHRP Web-Only Document 93 (http://trb.org/news/blurb_detail.asp?id=8858). Introduction and Research Approach 9

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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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