Study Details
Study Title: Safety Effectiveness of the Road Diet Treatment in Rhode Island
Authors: Zhou et al.
Publication Date: 2022
Abstract: A road diet is a low-cost countermeasure which typically involves converting an existing four-lane undivided roadway to a three-lane roadway, reducing the section to two through lanes and a center two-way left-turn lane. The objective of this evaluation was to estimate the safety effectiveness of road diets by developing a crash modification factor (CMF) specific to the U.S. state of Rhode Island. To account for potential selection bias and regression-to-the-mean, an empirical Bayes before-after analysis was conducted, using reference groups of untreated four-lane undivided roadways with similar characteristics to the treated sites. Results indicated a 29% decrease (CMF = 0.71) in total crashes and a 37% reduction in fatal and injury crashes (CMF = 0.63). The expected results of the evaluation will help Rhode Island Department of Transportation to determine a statewide direction for implementation of the countermeasure.
Study Citation: Zhou, Y., S. Himes, T. Le, J. Gooch, K. Northup, and P. Pasvao. "Safety Effectiveness of the Road Diet Treatment in Rhode Island". Transportation Research Record, DOI: 10.1177/03611981221076433, (2022).
CMFs Associated With This Study
Category: Roadway
Countermeasure: Road diet (Convert 4-lane undivided road to 2-lanes plus turning lane)
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.71 | 29 |  | All | All | All | All |
| 0.63 | 37 | | All | K,A,B,C | All | All |
