Can gps replace conventional travel surveys? Some findings

Global Positioning System (GPS) devices have been considered as a substitute for conventional travel diaries for some time. However, only in the past year has a serious effort been made to trial replacement of travel diaries with GPS. GPS devices are very accurate at recording the time and positional characteristics of travel, but cannot record travel modes, trip purposes, or number of occupants in private vehicles, all of which are important attributes normally acquired in a household travel survey. The authors of this paper have developed software that is able to deduce the missing data from a combination of the GPS records, other data collected from respondents, and data available in GIS records. However, the level of accuracy has not been checked. As part of an ongoing GPS-only survey, a prompted recall survey is being conducted on a sample of households. In this paper, we report on comparisons between the results from the processing software and the prompted recall web survey, with respect to identifying trips, modes and purposes of travel, and number of household members travelling together. These results will be used subsequently to develop refinements to the processing software.