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28 Standardized Procedures for Personal Travel Surveys 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 (00:0023:59). 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.