Safety Effectiveness of the Road Diet Treatment in Rhode Island

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.

Keywords

safety crash analysis crash modification factors (CMFs)crash prediction models

Get full access to this article

View all access options for this article.

References

Federal Highway Administration. Road Diets. FHWA-SA-17-066. U.S. Department of Transportation, Washington, D.C.https://safety.fhwa.dot.gov/provencountermeasures/pdfs/fhwasa17066.pdf.

Rhode Island Department of Transportation. Highway Safety Improvement Program 2019 Annual Report. Federal Highway Administration, Washington, D.C.https://safety.fhwa.dot.gov/hsip/reports/pdf/2019/ri.pdf.

Pawlovich

M. D.

Carriquiry

Welch

Iowa’s Experience with Road Diet Measures - Use of Bayesian Approach to Assess Impacts on Crash Frequencies and Crash Rates. Transportation Research Record: Journal of the Transportation Research Board, 2006. 1953: 163–171.

Harkey

D. L.

Srinivasan

Baek

Persaud

Lyon

Council

F. M.

Eccles

Lefler

Gross

Hauer

Bonneson

Crash Reduction Factors for Traffic Engineering and ITS Improvements. NCHRP Project 17-25 Final Report. National Cooperative Highway Research Program, Transportation Research Board, Washington, D.C., 2008.

Persaud

Lana

Lyon

Bhim

Comparison of Empirical Bayes and Full Bayes Approaches for Before-After Road Safety Evaluations. Accident Analysis and Prevention, Vol. 42, 2010, pp. 38–43.

Lyles

R. W.

Siddiqui

M. A.

Taylor

W. C.

Malik

B. Z.

Siviy

Haan

Safety and Operational Analysis of 4-Lane to 3-Lane Conversions (Road Diets) in Michigan. Report No. RC-1555. Michigan Department of Transportation, Lansing, 2012.

Abdel-Aty

M. A.

Lee

Park

Wang

Abuzwidah

Al-Arifi

Validation and Application of Highway Safety Manual (Part D) in Florida. Florida Department of Transportation, Tallahassee, 2014.

Sun

Rahman

Investigating Safety Impact of Center Line Rumble Strips, Lane Conversion, Roundabout and J-Turn Features on Louisiana Highways. Report No. FHWA/LA.18/597. Louisiana Department of Transportation and Development, Baton Rouge, 2019.

Hauer

Observational Before-After Studies in Road Safety: Estimating the Effect of Highway and Traffic Engineering Measures on Road Safety. Emerald Publishing Limited, London, 1997.

10.

Davis

G. A.

Accident Reduction Factors and Causal Inference in Traffic Safety Studies: A Review. Accident Analysis and Prevention, Vol. 32, 2000, pp. 95–109.

11.

Schafer

J. L.

Kang

Average Causal Effects from Nonrandomized Studies: A Practical Guide and Simulated Example. Psychological Methods, Vol. 13, No. 4, 2008, pp. 279–313.

12.

Rosenbaum

Rubin

The Central Role of the Propensity Score in Observational Studies for Causal Effects. Biometrika, Vol. 70, No. 1, 1983, pp. 41–55.

13.

Sasidharan

Donnell

Application of Propensity Scores and Potential Outcomes to Estimate Effectiveness of Traffic Safety Countermeasures: Exploratory Analysis Using Intersection Lighting Data. Accident Analysis and Prevention, Vol. 50, 2013, pp. 539–553.

14.

Holmes

W. M.

Using Propensity Scores in Quasi-Experimental Designs. SAGE, Thousand Oaks CA2013.

15.

Lord

Mannering

The Statistical Analysis of Crash-Frequency Data: A Review and Assessment of Methodological Alternatives. Transportation Research Part A: Policy and Practice, Vol. 44, 2010, pp. 291–305.

16.

Federal Highway Administration. Safety Performance Function Development Guide: Developing Jurisdiction-Specific SPFs. FHWA, Washington, D.C., 2013. https://safety.fhwa.dot.gov/rsdp/downloads/spf_development_guide_final.pdf.

17.

Persaud

Lyon

Empirical Bayes Before–After Safety Studies: Lessons Learned from Two Decades of Experience and Future Directions. Accident Analysis & Prevention, Vol. 39, No. 3, 2007, pp. 546–555.