Building Practical Origin-destination (od/trip) Matrices from Automatically Collected GPS Data
T van Vuren, Mott MacDonald and ITS, University of Leeds, UK; C Carey, Mott MacDonald, UK
We show how we have managed to create OD matrices from commercial data sources to replace or augment traditional survey methods such as roadside interviews. We discuss data issues such as bias and how to add purpose information.
Origin-destination matrices are key elements in transport models; however, they are costly to collect and process. Typical survey methods such as roadside interviews, or car park surveys, are expensive and disruptive. The instrument can introduce bias, by traveller avoiding the interview sites. Increasingly, authorities refuse to have live surveys on their roads due to Health and Safety concerns. Other methods for collecting origins and destinations, such as Automatic Number Plate Recognition and mailbacks to vehicle owners, suffer from privacy concerns.
However, data sources exist that are routinely collected, which contain inherent information on origins and destinations. These are the locational points of GPS Tracker services, produced by vehicles fitted with advanced GPS devices and collected by organisations like TrafficMaster and iTIS. As the vehicles poll every few seconds, a huge amount of travel data is in principle available, including origins and destinations of the equipped vehicles. This data has successfully been used in the past to generate speed maps for whole regions; the increasing rate of take up of these devices means that coverage and sample sizes are now such that more detailed analyses are possible.
We describe five applications where we have used commercially available, automatically collected GPS data to derive origin destination trip matrices. These are:
- developing HGV origin destination matrices
- investigation of ODs and routing patterns for evidence against a proposed Motorway Service Area
- trip distribution patterns of short trips (ie junction hopping) and through trips using the urban motorway network
- roundabout turning proportions study
- RSI stability analyses between different survey years
The applications give us an insight into data quality and sample sizes, resulting in us being able to advise on the applicability of automatically collected GPS data for the creation of OD trip matrices. We are currently investigating whether and how additional travel characteristics can be determined, for example trip purpose (from land uses at origin and destination, or from the timing and regularity of the trip).
Association for European Transport