Traffic conflicts analyses for 2+1 road sections

The additional passing lanes and 2+1 roads improve significant road safety. Studies indicate sections with additional passing lanes (relief or alternately), which may cause reduction in the number of accidents by 50%. However, how geometric design affects the safety performance of such sections is not in depth investigated. Previous studies are carried out with two approaches, i.e. the most often, based on analysis of observed crashes and more rarely by using microsimulation study. In the case of microsimulation research, traffic conflict theory can be applied as a surrogate measure of safety. One of the main problem in simulated conflicts study is the validation of simulation results against real world conditions. The aim of the paper is to assess the reliability of traffic conflict measures obtained by microsimulation against real world observation. Conflicts were detected and classified from video recording and analysis of vehicle trajectories in the merging area on 2+1 roads in Poland. Conducted studies focus only on lane changing conflicts, locations and TTCs values of observed conflicts between vehicles were primarily identified. Observed conflicts are than compared with microsimulated one, to assess if there is a correlation in the two.