Headway distribution effect on gap-acceptance behavior at roundabouts: driving simulator experiments in a case study

The main goal of this work is the analysis of gap-acceptance behavior at roundabouts under different types of headway distribution in the circulating stream through driving simulator experiments. The experiments were performed at the Transportation Laboratory of the University of Padova. The simulated scenario was first validated by reproducing the study site environment, a four-leg roundabout located in an urban area in northern Italy. Field and driving simulator lag/gap-acceptance data were used to estimate two values of mean critical gap. The comparison of these mean critical gaps was considered as a test to validate the driving simulator. Once the scenario had been validated, a driving simulator experiment was carried out to analyze the effect of vehicles arrivals distribution on drivers’ gap-acceptance behavior. The usefulness of this study is twofold. First, it supports the use of driving simulators as reliable research tools to reproduce drivers’ real gap-acceptance behavior at intersections; second, it demonstrates that the critical time gap of drivers at roundabout approaches depends strongly on the time headways distribution on the circulating roadway.