Simulation Study on the Effects of an Emission-Based Dynamic Freeway Control

Dynamic freeway control systems (FCS) aim to improve traffic safety and optimize vehicle flow on highly frequented freeway segments. This study considers emissions as an additional control objective. Various emission-based variable speed limit strategies and truck overtaking regulations are evaluated to mitigate air pollution resulting from traffic. To quantify the effects of an emission-based FCS, a microscopic traffic flow model of a section of freeway A5 near Frankfurt am Main, Germany, equipped with an FCS use. The conventional control algorithm is extended by integrating emission-based control programs into the model. The results show that emission reductions can be primarily attributed to two factors: first, the reduction in speeds, and second, the alleviation of congestion through stricter traffic harmonization. The study finds that the most significant potential for emission reductions occurs during periods of medium traffic flow rates, leading to a NOx reduction of up to 10% and a CO2 reduction of up to 6%.