Improved Speed Control Strategy for Mixed Traffic Flow Considering Roadside Unit

The information exchange among vehicles and road infrastructure with wide sensing range can be accomplished by roadside units (RSUs). Communication delays occur and are influenced by different approaches of deployment of RSUs, which increases the complexity of vehicle automatic control in a mixed traffic flow. Therefore, a speed control strategy was proposed for mixed traffic flow considering RSU deployment distance, interaction radius, and communication delay, aimed at enhancing traffic safety and efficiency. The characteristics of RSU deployment were modeled as functions, where an adaptive efficiency function was proposed to evaluate different RSU deployment plans. An improved speed control model was then developed based on the characteristics of the RSU in the mixed traffic flow. In addition, numerical analysis and simulation were carried out to evaluate vehicle stability and traffic throughput based on the improved speed control model. The analysis results show that the proposed model is stable under different updating frequencies, with the best stability achieved when the velocity update frequency is 500 and the velocity update time interval is 0.01 s. Moreover, it was found that the spatial occupancy rate increases with the increment of penetration rate of autonomous vehicles, which improves the rate by at least 20% compared to the no-control scenario. Additionally, the average speed is also increased by 30% while under the influence of communication delays. This paper investigated the relationship between characteristics of RSUs and traffic performances, which is essential for DOTs to develop an effective RSU plan to adapt to the mixed traffic flow.