Dynamic speed limit control to resolve shock waves on freeways - Field test results of the SPECIALIST algorithm

Abstract

We present the real-world test of the SPECIALIST algorithm in which dynamic speed limits were used to resolve shock waves on freeways. The real-world test was performed in the period September 2009–February 2010 on a 14 km long stretch on the Dutch A12 freeway. For the evaluation of the algorithm various performance measures were determined for each activation of the speed limits. The results show that the SPECIALIST algorithm can resolve shock waves in nearly 80% of the cases when the algorithm activated for shock waves. However, in approximately 50% of the activations the algorithm activated for jam types other than shock waves, in which case the effectivity was 40– 50%. Due to the tuning the stability of the traffic flow could be significantly improved, and the number of average activations per day was increased from 1.5 to 2.9 activations per day. The SPECIALIST algorithm was not only evaluated for traffic performance, but also for the correctness of the algorithm for real traffic in terms of expected qualitative behavior. Although the general operation of the algorithm is according to the theoretical expectations, some points for further improvements are identified during the test.