Study Details

Study Title: Effect of traffic roundabouts on accident rate and severity in Arizona

Authors: Mamlouk and Souliman

Publication Date: 2019

Abstract: Although roundabouts have been used at many locations around the world, the safety of roundabouts under different conditions has not been fully understood. In this study, 17 roundabouts in five cities in Arizona were evaluated, out of which 11 are single lane and six are double lane. Most of the intersections of single lane roundabouts were controlled by two-way stop signs before roundabout conversion, whereas most of the intersections of double-lane roundabouts were controlled by traffic signals. Accident data were collected and broken down into five categories: damage without injury, minor injury, non-incapacitating injury, incapacitating injury, and fatality. Equal number of years were used before and after the roundabout conversion at each location. The average rates of accidents, damages without injury, injuries and fatalities per year and per million vehicles were evaluated. It was found that single-lane roundabouts reduced the accident rate, whereas double-lane roundabouts increased the accident rate. The results also showed that single- and double-lane roundabout conversions reduced the severity levels of accidents. Considering accident rate and severity level, warrants need to be developed for roundabout conversion and number of roundabout lanes under different traffic conditions.

Study Citation: Mamlouk, M., and B. Souliman. "Effect of traffic roundabouts on accident rate and severity in Arizona". Journal of Transportation Safety and Security, Vol. 11, No.4 (2019), pp.430-442.

CMFs Associated With This Study

Category: Intersection geometry

Countermeasure: Conversion of intersection to roundabout

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.9642 StarsAllONot specifiedUrban
0.64362 StarsAllB,CNot specifiedUrban
0.42582 StarsAllK,ANot specifiedUrban
1.55-552 StarsAllAllNot specifiedUrban
1.67-672 StarsAllONot specifiedUrban
0.9372 StarsAllB,CNot specifiedUrban
0.33672 StarsAllK,ANot specifiedUrban
0.82182 StarsAllAllNot specifiedUrban
1.02-22 StarsAllONot specifiedUrban
0.56442 StarsAllB,CNot specifiedUrban
0.37632 StarsAllK,ANot specifiedUrban
1.62-622 StarsAllAllNot specifiedUrban
1.6-602 StarsAllONot specifiedUrban
0.89112 StarsAllB,CNot specifiedUrban
0.16842 StarsAllK,ANot specifiedUrban