Abstract

Achieving the maximum utilization of the existing infrastructure is an essential goal of traffic management for both freeways and the urban road network. Reliable and explicit information about the current traffic condition are required for using the road network efficiently. So far, the lack of a uniform classification scheme results in a time consuming process of coordination between different stakeholders developing and implementing control strategies and providing traffic information. In this study, a uniform concept is developed defining the traffic conditions on freeways and urban roads. This classification scheme is applicable for all stakeholders (e.g. road authorities, broadcasting services, private service providers) and can be used in both infrastructure-based and vehicle-based applications. In order to determine an appropriate traffic flow parameter for a comprehensible representation of the traffic condition, extensive data from freeways and urban roads in Germany were collected and analyzed. The empirical basis is provided by segment-based and local data obtained with different detection methods. As expected, the average speed per segment leads to a more precise description of the traffic condition than local speed values from stationary detectors. Test runs with probe vehicles were made using a GPS tracking device to record the floating cars driving speed. During the test runs, a subjective evaluation of the traffic flow quality was provided by different passengers (probands) in the vehicle. In total, over 15000 sets of travel speed data with associated grading of the experienced traffic flow quality were analyzed to develop a six-step classification scheme. Based on different approaches, threshold values of the average travel speed were determined depending on the type of road and the speed limit. This uniform classification scheme can offer valuable decision guidance for traffic management strategies. For providing more comprehensible traffic information for the road users, the developed scheme was transferred to a three-step system, easily illustrated by the colors green, yellow and red.