The USA's 1991 Intermodal Surface Transportation Efficiency Act (ISTEA) provides an organised and effective strategy for traffic congestion control and transport efficiency. The key procedures of all ISTEA's management systems are the accurate measurement and evaluation of highway operations, performance, cost-benefit relations, and leading trends. A vital part is played here by advances in data collection and presentation, including satellite global positioning systems (GPS) and geographical information systems (GIS). This paper presents the GIS-based congestion management system developed for the City of Novi in the Detroit Metropolitan Area, MI, USA. Extensive data on traffic flows, roadway geometries, and accidents were collected as part of the project. Measurements were made of the operation characteristics of traffic flow, volume-to-capacity characteristics, and freedom-of-movement characteristics. A complete level-of-service (LOS) analysis was performed for all major junctions and road segments in the city. Average travel speeds and stop time delays per vehicle are tabulated for six levels of service at signalised junctions.
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