Evaluation of intersection conflict warning system at unsignalized intersections: A review

Unsignalized intersections are identified as the critical locations due to higher number of road crashes at these locations. The primary causes of crashes at unsignalized intersections are limited sight distance, incorrect assessment of gaps by drivers on the minor road, and higher speeds of vehicles on the major road. In an effort to improve safety and reduce the severity of crashes at unsignalized intersections, an intelligent transportation system (ITS) called the intersection conflict warning system (ICWS) has been developed. The ICWS consists of an activated warning sign and sensors that detect vehicles approaching the intersection. This paper aims to summarize the performance evaluation of ICWS that has been published in the literature. The review commences with an overview of the purpose of designing and installing ICWS at unsignalized intersections. It then discusses driving performance measures considered to evaluate the effectiveness of ICWS in three different environments, i.e., real world, driving simulator, and simulations, and their results are presented. The paper also discusses the type of sensors used to detect vehicles approaching the intersection and their accuracy in vehicle detection. The results reveal that ICWS had substantially improved driver behaviour. In the presence of ICWS, drivers resulted in shorter reaction time, lower approach speed, increased critical gap acceptance, and reduction in conflicts. An improvement in the performance of ICWS can be achieved by educating drivers about the sign, maintaining system reliability, and further examining the effect of various traffic factors, driver factors, and environmental factors on ICWS. The findings of this study can help researchers and engineers to design a better ICWS that can greatly enhance driving performance and safety at unsignalized intersections.