Speed Harmonization

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Speed Harmonization

Evaluation of Effectiveness Under Congested Conditions

Talebpour, Alireza / Mahmassani, Hani S. / Hamdar, Samer H.

The objective of this study was to explore the impacts of early shock wave detection on breakdown formation and driving hazards (safety) and the possible corresponding improvements from the use of speed harmonization as a control strategy. Several efforts have been made to evaluate speed harmonization systems by means of various traffic microsimulation models. However, further related behavioral-based studies are needed, especially in light of the development of connected-vehicle technology. The adopted approach relies on a cognitive risk-based microscopic simulation model capable of endogenously accounting for incidents to study the effects of speed harmonization strategies on traffic flow characteristics and safety. An algorithm based on wavelet transform—to detect shock wave formation—was combined with a reactive speed limit selection algorithm to implement speed harmonization within the microscopic simulation model. Three sets of scenarios were simulated. The results showed significant improvement in traffic flow characteristics through the implementation of the speed harmonization control strategy under congested conditions. Analysis of a fundamental diagram revealed the existence of an optimal location to implement the speed limit changes upstream of the point of shock wave detection. The analysis also revealed the role of speed limit compliance for the success of a speed harmonization system.