Impact Evaluation of a Driving Support System on Traffic Flow by Microscopic Traffic Simulation

In this study, we estimated dangerous traffic situations by installing a driving support system and using a microscopic traffic simulation which was modified by adding the function of perception-response process. In this approach, a dangerous situation is assessed by detecting conflict through simulation. For this assessment, a safety indicator named TIDSS (Time Integral of Difference of Space distance and Stopping distance) was defined from the time integral of the relative distance between the leading and following vehicle when the leading vehicle brakes suddenly. This indicator is superior to existing indicators because it can evaluate any type of situation and consider the degree and duration of danger for each vehicle. The proposed approach was applied to evaluate the adaptive cruise control system (ACC) and automated platoon system (APS) for heavy trucks on the Tokyo metropolitan expressway. To evaluate the impact of ACC and APS on traffic flow, many cases with different installation rates of ACC and APS were simulated using the proposed approach, and the relation between installation rate, safety indicators, and traffic flow rate was analyzed. Thus, we found that the introduction of ACC might mitigate dangerous situations on the expressway by decreasing the traffic flow rate. In contrast, introduction of APS might mitigate dangerous situations and increase the traffic flow rate.