Variable speed limit control based on the extended link transmission model

Reference:
M. Hajiahmadi, R. Corthout, C. Tampère, B. De Schutter, and J. Hellendoorn, "Variable speed limit control based on the extended link transmission model," Proceedings of the 92nd Annual Meeting of the Transportation Research Board, Washington, DC, 15 pp., Jan. 2013. Paper 13-0409.

Abstract:
In this paper, the link transmission model (LTM) is extended to include the effects of variable speed limits (VSL) and consequently to provide variable speed limit control for traffic networks modeled by LTM. The LTM has recently been developed for route assignment, but in this paper the LTM is modified to be used for control purposes. By this we achieve a model that provides a balanced trade-off between accuracy and computational complexity, and hence it is useful for on-line model-based traffic control. Nevertheless, the extension of the model for ramp metering and speed limit control needs careful attention. Since the LTM lacks explicit velocity equations focus is on other potential sources that could imitate the influences of VSL. The delays inside the model are manipulated in order to achieve the mentioned goal. Moreover, we take into account different situations that may occur in reality based on changes in VSL and different traffic conditions. Finally, the total extensions are verified using simulation and real data. To this aim, the VSL extension integrated in the LTM is verified using simulations for a benchmark case study (in order to show performance of the extended LTM clearly). Next, the LTM is calibrated by real data collected from the A12 Freeway in The Netherlands. The optimal parameters of the model are identified using a global optimization method. Comparison with real data from a period of time that VSL installed on the freeway are active, shows acceptable performance of the total extended and calibrated LTM.