Statistical Analysis of Two-lane Roundabout Data for Traffic Control Decision-Making in an Urban Area

Researches using existing statistics and data collected from the area of study help officials at decisionmaking, to improve the region's problems, like the problem of the high rate of accidents in the region, despite the low volume of daily service. The uses of roundabouts in many parts of the world have many advantages over intersections, amongst them are increased safety and capacity and reduced cost. To improve roundabout function, roundabout traffic control and vehicle safety, informed decisionmaking from studies carried out is required. Roundabout design for Capacity and safety are inseparable components, due to the conditions of roundabout geometry, traffic sign, pavement conditions and patterns of driver’s behavior change. The aim of this study was to evaluate the importance and influence of these parameters on the behavior of drivers. In this research, the effect of Pavement Condition Index (PCI), Contrast of roundabout lane lines color and volumetocapacity ratio on the value of obeying the rules of the road for drivers (using turn signals and avoiding unnecessary lane change at roundabout) were evaluated. Data was gathered through field research of seven roundabouts in the city of Yazd, Iran. Statistical methodologies (ttest method and bivariate regression) and the CART model were used for data analysis. Results show when Pavement Condition Index (PCI) improves, unnecessary lane changes by drivers at the roundabout decrease. Similarly, the use of turn signal increases with an increase in the volumetocapacity ratio, so in the roundabouts with a higher volumetocapacity ratio of 0.58, 47.5% of drivers use turn signals, while with a less volumetocapacity ratio of 0.58, the rate of using turn signal will be less than this amount (11.7%).This suggests the need for policymaking at roundabout with low volumetocapacity ratio, to encourage the use of turn signals by drivers. The results of this research can help city managers and traffic police to prioritize traffic control and reform municipal roundabouts.