| Transportation planners conduct travel surveys to collect data needed as input to travel demand models, which are used to forecast the need for road and transit enhancements and expenditures. Travel surveys are conducted using a combination of paper trip diaries for data collection and computer-assisted telephone interviews (CATI) for data retrieval. Recently, several pilot studies have combined Global Positioning System (GPS) technology with travel survey data collection to evaluate opportunities for improving the quantity and accuracy of travel data. These studies used GPS to supplement the traditional data elements collected in paper or electronic travel diaries.; This dissertation presents the results of a proof-of-concept study that examined a new opportunity for using GPS technology in travel surveys—that is, the use of GPS data collection to completely replace, rather than supplement, traditional travel diaries. The challenge in this new approach is to process the GPS data in a manner such that most of the traditional trip data elements can be derived. If this processing is done correctly and quickly, then the CATI retrieval call, which is used to collect household, person, vehicle and travel information, could be modified so that the only travel questions asked would be those necessary to clarify any uncertainties in the processed GPS travel data and to collect any missing elements. This process would not only improve the quality and robustness of the data, but would also greatly reduce respondent burden and telephone interview times.; This study was conducted using GPS data loggers to collect travel data in personal vehicles. The GPS data were then processed within a Geographic Information System (GIS) to derive most of the traditional travel diary elements. These derived data were compared with the data recorded on paper diaries by the same survey participants and were found to match or exceed the reporting quality of the participants. In fact, the GPS data revealed trips that were not recorded by the participants. Most importantly, this research demonstrates that it is feasible to derive trip purpose, the one element that has been considered “underivable”, from GPS data by using accurate GIS databases. |
