Impact of travel survey advance letter on trip underreporting and number of calls required for survey completion

In household travel behavior surveys, trips made by household members not directly responding to the survey are often underreported by the responding household member. Given the significant impact that such underreporting of trips could ultimately have on transportation infrastructure investment decisions, underreporting of trips has received considerable research attention. The research reported in this thesis builds on previous research by investigating an element of the travel survey process, the survey advance letter, to determine its impact on trip underreporting and on the number of calls required to complete the survey of a household.;The study approach consisted of a review of the relevant literature followed by a statistical analysis of the study-data to determine which variables were associated with the number of trips reported to be made by the members of household and the number of calls made to complete the survey respectively. The study results show that the advance-letter status of a household, after adjusting for proxy interviewing, has a significant impact on the number of trips reported to be made by each of a household's members. Further, it is also found to have a significant impact on the number of calls made to successfully complete the survey. It is recommended that in the conduct of household travel behavior surveys, attention be given to measures that will ensure that these letters reach the correct sampled households and are read upon delivery. It is also recommended that appropriate trip adjustment factors be developed to adjust the trip-rates of persons from households that did not receive the survey advance letter.