Integration of the global positioning system and geographical information systems for traffic congestion studies

The Transport Systems Centre (TSC) has developed an integrated Global Positioning System (GPS)–Geographical Information System (GIS) for collecting on-road traffic data from a probe vehicle. This system has been further integrated with the engine management system of a vehicle to provide time-tagged data on GPS position and speed, distance travelled, acceleration, fuel consumption, engine performance, and air pollutant emissions on a second-by-second basis. These data are handled within a GIS and can be processed and queried during the data collection (from a notebook PC in the vehicle) or saved to a file for later analysis. The database so generated provides a rich source of information for studies of travel times and delays, congestion levels, and energy and emissions. A case study application of the system is described focusing on studies of congestion levels on two parallel routes in a major arterial corridor in metropolitan Adelaide, South Australia. As part of these investigations, a discussion of the nature of traffic congestion is given. This provides both a general definition of traffic congestion and the discussion of a number of parametric measures of congestion. The computation of these parameters for the study corridor on the basis of data collected from the integrated GPS–GIS system is described. The GIS provides a database management platform for the integration, display, and analysis of the data collected from GPS and the in-vehicle instrumentation.