Exploring the Use of Passive GPS Devices to Measure Travel

Global Positioning System devices are emerging as a potential means to collect improved data on the spatial aspects of personal travel. In many applications, the GPS device is coupled with a Personal Data Assistant of some type and the respondent who is using the GPS device is required to enter various data items at the start of each trip made with the device. This procedure has the disadvantage that it relies on the memory of the respondent to use the PDA, and also is subject to being missed if the respondent is in a hurry. This paper builds on earlier work by Stopher and others to develop a passive GPS device, for which additional non- GPS data may be added either through inference or through a subsequent prompted recall survey. The paper describes the use of both in-vehicle and personal versions of a GPS device that logs position in one- or five-second intervals and has a number of other capabilities, such as turning off automatically when speed drops below 1 knot. Experiments have been performed in which the devices are tested for a range of different situations, including collecting data for one month, collecting data on trains, buses, and ferries, and experimenting with automatic on/off procedures. The paper reports on a number of experiments, describes the procedures undertaken to download and analyse the data, and processing of the data for the prompted recall surveys. Initial results are included on experiments with the prompted recall, and options to develop this as an internet survey are explored. In addition, analysis of the data is conducted to investigate congestion and the amount of time spent under congested travel conditions. Potential applications of this analysis to a variety of purposes is described in the paper