Development of a Root Cause Degree Procedure for measuring intersection safety factors

Abstract China has long ranked first in the world in the number of road accidents and fatalities, approximately 30% of which occurred at urban intersections. Therefore, measuring intersection safety factors is essential to achieve effective correction countermeasures. A Root Cause Degree Procedure (RCDP) to measure intersection safety is proposed. The idea behind RCDP is to prevent the likelihood of a problem’s reoccurrence based on root cause analysis. It combines the DEMATEL (Decision Making Trial and Evaluation Laboratory) method and fuzzy logic to determine quantified measures. The root cause factor can be clearly visualised and differentiated using the Root Cause Degree (RCD) diagram. The factors with the largest RCD should be improved for greater benefit-cost ratio at limited traffic financial investment. The method uses the accident risk degree as an evaluation index based on risk analysis, which is independent of crash data, and is suitable for current incomplete crash data sets, such as those from developing regions of China. Additionally, the Shanghai municipality is used as an example for the pilot analysis. The current root cause factors in order of frequency of occurrence are clearance time, safety education, enforcement, the trajectory inside the intersection, crossing a refuge island, speeding, and the right turn control pattern. These factors should be corrected to improve safety performance. These results are consistent with actual traffic conditions according to current engineering practices, which indicates the feasibility of the proposed method.