Analysis of 28-day global positioning system panel survey: Findings on variability of travel

The Institute of Transport and Logistics Studies at the University of Sydney, Australia, has pioneered the use of the Global Positioning System (GPS) as a means of measuring personal travel in Australia. The results of a 28-day GPS survey of 50 households are reported, specifically in terms of variability in the daily travel of individuals. The first evidence examined is the frequency with which people stay at home all day, because it often has been suggested as a possible measure of survey quality and because it is fairly easy for people to decide to leave the GPS device at home on certain days or to forget to take it with them during a GPS survey. Next, the actual variability in daily travel is examined by looking at the variability in the means and variances of daily passenger kilometers of travel, daily number of trips, average travel time per trip, average distance per trip, and total travel time per day. Subsequently, the proportions of variance that arise from intrapersonal variability and interpersonal variability are examined.