Enhancing Traffic Efficiency and Sustainability through Strategic Placement of Roadside Units and Variable Speed Limits in a Connected Vehicle Environment

With the deployment of cooperative intelligent transportation systems (C-ITSs), the telecommunication systems and their performance occupy a key position in ensuring safe, robust, and resilient services to the end-users. Regardless of the adopted protocol, adequate road network coverage might affect the service performance, in terms of traffic and environmental efficiency. In this study, we analyze the traffic efficiency and emission pollutant sensitivity to the location of ad hoc network antennas when the C-ITS services disseminate dynamic messages to control the speed limit and ensure sustainable mobility. We design the experimentation with short-range communication resulting from an ad hoc network and requiring Roadside Units (RSUs) along the road to broadcast messages within their communication range to the end-user. The performance variability according to the RSUs' location and effective road network coverage are highlighted through our microscopic simulation-based experimentations. This paper develops a sensitivity analysis to evaluate the impact of the network mesh according to the C-ITS service under consideration. Focus is placed on the variable speed limit (VSL) service, controlling upstream speed to restrict congestion and ensure more sustainable mobility. The results show that, while the traffic efficiency improves even at a low market penetration rate (MPR) of the connected vehicles, the environmental efficiency improves only at a high MPR. From the telecommunication perspective, an expansive broadcast strategy appears to be more effective than the conservative approach.