Safety Effectiveness and the Role of Geometric, Traffic, and Crash History–Related Factors in Converting a Stop-Controlled Intersection to a Miniroundabout

Abstract

The focus of this paper is on evaluating the safety effectiveness of converting a stop-controlled intersection with a speed limit≥56.3 km/h (35 mi/h) to a miniroundabout and examining the role of influencing factors on their safety effectiveness in the United States. Crash, traffic volume, and geometry data for 25 miniroundabouts in eight states was collected to conduct before–after analysis using the empirical Bayes (EB) method. In addition, crash and traffic volume data for 723 reference intersections were gathered and used for computing the calibration factors and developing jurisdiction-specific safety performance functions (SPFs). A 19.63% and 60.55% reduction in the number of total crashes and fatal and injury (FI) crashes but an 7.72% increase in property damage only (PDO) crashes was observed when a two-way/one-way stop-controlled (TWSC/OWSC) intersection was converted to a miniroundabout. A 224.76%, 74.30%, and 282.71% increase in the number of total crashes, FI crashes, and PDO crashes was observed when an all-way stop-controlled (AWSC) intersection was converted to a miniroundabout. Converting a TWSC/OWSC intersection to a miniroundabout has better safety benefits than converting an AWSC intersection to a miniroundabout. The recommended crash modification factors (CMFs) for converting a TWSC/OWSC intersection to a miniroundabout are 0.80, 0.39, and 1.08 for total, FI, and PDO crashes. The recommended CMFs for converting an AWSC intersection to a miniroundabout are 3.25, 1.74, and 3.83 for total, FI, and PDO crashes. The number of crashes in the before period, cross-street traffic volume, speed limit at major street and cross-street, and intersection skewness have a statistically significant influence on the safety effectiveness of miniroundabouts at a 90% confidence level. These findings are useful to researchers and practitioners for conducting safety benefit analysis and making informed decisions pertaining to converting a stop-controlled intersection to a miniroundabout.