Effects of Rainfall on Driver Behaviour and Gap Acceptance atMultilane Roundabouts

Background:This paper filled an important gap in the behaviour of driver and gap acceptance model at multilane roundabouts by investigatingtheir traffic performances during rainfall. Introduction:The study carried out an investigation into the impact of rainfall on driver’s behavioural changes and gap acceptance characteristics.Follow-up time headway and gap time were used as proxies. Methodology:Traffic volume, speed, vehicle type and headway data were collected at selected multilane roundabouts in Durban, South Africa. Allsurveyed roundabouts are within rain gauge catchment area of about 1km. Rainfall intensity was divided into three groups (light,moderate, and heavy). Dry weather data were used as control parameters.Data Analysis:Stepwise data analytical technique was used for ease of explanation and clarity. All model equations were tested for statistical fitnessand deemed satisfactory for further analysis. Conclusion:Based on the synthesis of evidence obtained from driver’s behavioural changes and gap acceptance characteristics at multilaneroundabouts, the paper concluded that it is correct to suggest that rainfall would have a profound effect on follow-up time headwayand critical gap acceptance. However, the effect diminishes gradually as volume to capacity ratio approaches peak traffic operation.Once the threshold value of 0.85 is reached the diminishing effect of rainfall as the sole actuator of anomalous time headway increaseis noticeable.