Household Travel Surveys with GPS An Experiment

This paper documents the results of a pilot test done for the Oregon Household Travel Survey. The pilot was designed to enable the Oregon Department of Transportation to determine the role of a Global Positioning System (GPS) in the upcoming survey effort. Specifically, a three-pronged approach was employed. Households were randomly selected for inclusion in the study and then assigned to one of three groups: (a) the traditional survey approach, (b) the traditional approach with GPS, and (c) GPS only. A total of 299 households from the city of Portland, Oregon, were recruited into the pilot, with 235 completing all required activities. A comprehensive evaluation of the similarities and differences in results across the three groups showed differences in respondent burden, completeness of travel details obtained, and costs. Results from this experiment also showed differences in nonresponse bias. The traditional survey had an expected nonresponse for the large households, low-income households, and young adults. Minority participation was on par with census figures. The GPS groups showed higher participation rates for young adults and nonminorities. These data confirmed the general thought that GPS was an effective tool for mitigating nonrespouse among young adults. However, the minority nonresponse bias increased significantly with technology, suggesting that other methods would be more appropriate. With regard to completeness of data, geocoding rates are higher for the GPS groups, and there are significant differences in trip departure times, which could affect peak hour and time-of-day modeling. As expected, the costs were higher for the GPS groups, but the expectation is that these costs will fall as processes are standardized across studies and new technologies are introduced.