Paper presented at the 28th Annual Southern African Transport Conference 6 - 9 July 2009 "Sustainable Transport", CSIR International Convention Centre, Pretoria, South Africa.
Global Positioning Systems (GPS) were used to track individuals and the results were compared with traditional pen and paper based travel surveys. The objective was to assess the capability of GPS to replace or, alternatively, to complement the traditional travel survey or diary. Small, nonintrusive GPS units were distributed to 130 respondents in the Western Cape. The respondents were also asked to complete a travel survey for the period of tracking. The results of the two techniques-were compared on issues such as origin and destination of the trips, routes taken, total number of trips and tours, and type of information delivered. GPS tracking delivered accurate information on the origin and destination of trips, routes taken, number of trips and tours and with additional examination, on the transport mode used. Comparing GPS and traditional surveys showed that GPS captured significantly more trips and tours originating from home and work.
These 'missed' trips in the diary are often shorter walks or 'strolling' trips. It was also found that respondents tend to round off their trip departure and arrival times and under-estimate trip duration. Generally, it was felt that the diary accurately recorded the work activity and the normal routine but did not capture short trips linked to the work trip. While GPS devices do deliver adequate information, the cost of the technology, the programming involved to extract information from the large datasets, and the auxiliary requirements, do not make GPS travel surveys an alternative to traditional techniques in the short term. The current role of GPS is more as validation or providing expansion factors for larger surveys on, for example, trip generation and route choice.
