TRB's National Cooperative Highway Research Program (NCHRP) Research Results Digest 400: Sample Size Implications of Multi-Day GPS-Enabled Household Travel Surveys summarizes an NCHRP project that studied the design of household travel surveys. Multi-day travel surveys are now more feasible, given global positioning system (GPS) technology. This project explores if surveys using a GPS device provides less drop-off in response compared to travel diaries. This project also investigates the effects of using multi-day data for developing travel demand models and explores the impact of sample size on multi-day versus single-day surveys. This digest summarizes key findings of research conducted in NCHRP Project 08-36/Task 123, "Survey Sample Size and Weighting." The appendixes to the project's final report are available to download from the TRB website.
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