TRAFFIC SAFETY ASSESSMENT BY USING MICRO-SIMULATION MODELLING AND TRAFFIC CONFLICTS AT LARGE ROUNDABOUTS

Abstract

Recent research has shown that traffic conflicts provide useful insight into the failure mechanism that leads to road collision between vehicles while being more frequent than accidents and without social cost. This paper provides proactive quantitative evaluation of traffic safety on three design layouts of large roundabouts by using microscopic traffic simulation approach. Combination of VISSIM and Surrogate Safety Assessment Model (SSAM) were used to model variant roundabouts with atypical layouts and assess traffic safety. The roundabouts were assessed by two approaches: (1) surrogate safety indicators - Time to Collision (TTC) and Post encroachment time (PET) and (2) safety assessment methods (reflecting severity of conflicts and potential collisions). Based on comparison of the results achieved by both methods and generally accepted safety principles were submitted proposals and recommendations for practical use of the proactive traffic safety assessment methods with surrogate safety indicators.