The benefits of measuring driving exposure using objective GPS-based methods and subjective self-report methods concurrently

Measurement of individualsr driving exposure has traditionally relied on subjective self-report methods, which tend to be inaccurate and require substantial effort for the individuals volunteering for the study. The development of Global Positioning System (GPS) technology has provided a new option for accurately and objectively measuring exposure. However, some exposure information (trip purpose and driver identification) can most easily be obtained with self-report methods. Therefore, the purpose of this study was to evaluate the concurrent use of GPS data loggers and telephone-based travel diaries for measuring driving exposure. The driving of 54 participants (aged = 75) was monitored for a period of one week. The GPS data loggers provided standard exposure measures (distance driven, time spent driving, number of trips), as well as measures that cannot be obtained through self-report (travelling speed, driving route) for all participants. The distance measured by GPS corresponded with distances obtained from the odometers in the vehicles, which indicated that the GPS measurements were accurate. Furthermore, the trips that were recorded by GPS were matched to the information reported in the travel diaries and, therefore, the purpose and driver of a majority (95.2 per cent) of the trips could be identified. Also, a subset of the participants who were interviewed (n = 16) provided favourable feedback regarding the data collection process. The findings indicate that GPS technology will advance the measurement of driving exposure but that self-report methods are still useful for obtaining certain exposure information. Therefore, GPS technology may not replace traditional methods but complement them.