Safety Assessment of Uncontrolled Intersections Using Both Conflict Probability and Severity

This paper presents a method to assess the safety of uncontrolled intersections considering both conflict probability and severity, which are two major properties of traffic conflicts. This method provides not only the safety level of the entire intersection but also the distribution of safety within intersections. Intersections are modelled by a two-dimensional Cartesian coordinate system and the internal space of intersections is divided into cells. Firstly, vehicle movement characteristics of at uncontrolled intersections are modelled. Secondly, conflict probability of each cell within the intersection is estimated considering approaching probability and lateral migration probability of vehicles. The quantification of conflict severity is based on kinetic energy loss of potential crashes. Grey cluster analysis is used to combine conflict probability and severity to model the safety assessment of each cell. Thirdly, the application of this method discussed, and an overall safety index of intersections is proposed considering weighted safety level and relative value of area with different safety levels. Finally, a case study, which includes three different designs, is presented along with visualization technique to demonstrate the results. The results not only show the validity of the model, but also indicate that the proposed method can be applied for: i) safety evaluation of existing or designed intersections; ii) dangerous position management within intersections; iii) safety assessment of designed intersections and iv) safety level comparison among different intersections or various designs for the same intersection. Using this method, engineers and planners can better evaluate and improve the safety of existing or the future uncontrolled intersections. The future work will use this approach to develop the models of other types of intersections and different road users.