Empirical Bayes Before–After Study on Safety Effect of Narrow Pavement Widening Projects in Texas

Abstract

Texas has approximately 40,000 lane miles (64,000 lane kilometers) of two-lane farm-to-market (FM) and ranch-to-market (RM) roads with total paved widths of 18 to 22 ft (5.5 to 6.7 m), most of which are in rural areas. Narrow pavement widening in Texas typically involves adding lane width, a narrow shoulder, or both to increase the travel way in each direction of a narrow FM and RM road by 1 to 9 ft (0.3 to 2.7 m). The main reasons for roadway widening are usually to do any or all of the following: improve safety, increase structural capacity, and enhance pavement performance. The goal of this study was to investigate the safety effects of narrow pavement widening projects for rural two-lane FM and RM roads in Texas. A before–after comparison study was conducted with the empirical Bayes method to evaluate how wider lanes and shoulders affect crash occurrence, by type and severity. Of the 22 studied projects, analysis showed a 31.5% reduction in total crashes, a 35.7% reduction in run-off-the-road crashes, and a 55.4% reduction in head-on crashes after narrow widening projects were carried out. The projects were also effective in reducing fatal crashes and injuries by about 29.5%. These findings suggest that pavement widening is an effective safety countermeasure on narrow two-lane FM and RM roads in rural areas.

Get full access to this article

View all access options for this article.

References

Burton

, Kim

M. Y.

, Smit

, Trevino

, Wu

, Murphy

, and Prozzi

. Flexible Pavement Narrow Widening Best Practices and Lessons Learned. FHWA/TX-14/0-6748-2. Center for Transportation Research, University of Texas at Austin, 2014.

Griffin

L. I.

, and Mak

K. K.

. Benefits to Be Achieved from Widening Rural, Two-Lane Farm-to-Market Roads in Texas. Presented at 67th Annual Meeting of the Transportation Research Board, Washington, D.C., 1988.

Zegeer

C. V.

, Deen

R. C.

, and Mayes

J. G.

. Effect of Lane and Shoulder Widths on Accident Reduction on Rural, Two-Lane Roads. In Transportation Research Record 806, TRB, National Research Council, Washington, D.C., 1981, pp. 33–43.

Zegeer

C. V.

, Stewart

, Council

, and Neuman

. NCHRP Report 362: Roadway Widths for Low-Traffic-Volume Roads. TRB, National Research Council, Washington, D.C., 1994.

Zegeer

C. V.

, Reinfurt

D. W.

, Hummer

, Herf

, and Hunter

. Safety Effects of Cross-Section Design for Two-Lane Roads. In Transportation Research Record 1195, TRB, National Research Council, Washington, D.C., 1988, pp. 20–32.

Bayesian Multivariate Poisson-Lognormal Regression for Crash Prediction on Rural Two-Lane Highways. PhD dissertation. University of Texas at Austin, 2006.

Hadi

M. A.

, Aruldhas

, Chow

L.-F.

, and Wattleworth

J. A.

. Estimating Safety Effects of Cross-Section Design for Various Highway Types Using Negative Binomial Regression. In Transportation Research Record 1500, TRB, National Research Council, Washington, D.C., 1995, pp. 169–177.

Harwood

D. W.

, Council

F. M.

, Hauer

, Hughes

W. E.

, and Vogt

. Prediction of the Expected Safety Performance of Rural Two-Lane Highways. FHWA-RD-99-207. FHWA, Washington, D.C., 2000.

Gross

, and Jovanis

P. P.

. Estimation of Safety Effectiveness of Changes in Shoulder Width with Case Control and Cohort Methods. In Transportation Research Record: Journal of the Transportation Research Board, No. 2019, Transportation Research Board of the National Academies, Washington, D.C., 2007, pp. 237–245.

10.

Bonneson

, Lord

, Zimmerman

, Fitzpatrick

, and Pratt

. Development of Tools for Evaluating the Safety Implications of Highway Design Decisions. FHWA/TX-07/0-4703-4. Texas Transportation Institute, Texas A&M University System, College Station, 2007.

11.

Gross

, Jovanis

P. P.

, and Eccles

K. A.

. Safety Effectiveness of Lane and Shoulder Width Combinations on Rural, Two-Lane, Undivided Roads. In Transportation Research Record: Journal of the Transportation Research Board, No. 2103, Transportation Research Board of the National Academies, Washington, D.C., 2009, pp. 42–49.

12.

Schrock

S. D.

, Parsons

R. L.

, and Zeng

. Estimation of Safety Effectiveness of Widening Shoulders and Adding Passing Lanes on Rural Two-Lane Roads. In Transportation Research Record: Journal of the Transportation Research Board, No. 2203, Transportation Research Board of the National Academies, Washington, D.C., 2011, pp. 57–63.

13.

Hauer

Observational Before–After Studies in Road Safety: Estimating the Effect of Highway and Traffic Engineering Measures on Road Safety. Pergamon, Tarrytown, N.Y., 1997.

14.

Hauer

, Harwood

D. W.

, Council

F. M.

, and Griffith

M. S.

. Estimating Safety by the Empirical Bayes Method: A Tutorial. In Transportation Research Record: Journal of the Transportation Research Board, No. 1784, Transportation Research Board of the National Academies, Washington, D.C., 2002, pp. 126–131.

15.

Persaud

B. N.

, Retting

R. A.

, Garder

P. E.

, and Lord

. Safety Effect of Roundabout Conversions in the United States: Empirical Bayes Observational Before–After Study. In Transportation Research Record: Journal of the Transportation Research Board, No. 1751, TRB, National Research Council, Washington, D.C., 2001, pp. 1–8.

16.

Harwood

D. W.

, Bauer

K. M.

, Potts

I. B.

, Torbic

D. J.

, Richard

K. R.

, Rabbani

E. R. K.

, Hauer

, Elefteriadou

, and Griffith

M. S.

. Safety Effectiveness of Intersection Left- and Right-Turn Lanes. In Transportation Research Record: Journal of the Transportation Research Board, No. 1840, Transportation Research Board of the National Academies, Washington, D.C., 2003, pp. 131–139.

17.

Montella

Safety Evaluation of Curve Delineation Improvements Empirical Bayes Observational Before-and-After Study. In Transportation Research Record: Journal of the Transportation Research Board, No. 2103, Transportation Research Board of the National Academies, Washington, D.C., 2009, pp. 69–79.

18.

Azizi

, and Sheikholeslami

. Safety Effect of U-Turn Conversions in Tehran: Empirical Bayes Observational Before-and-After Study and Crash Prediction Models. Journal of Transportation Engineering, Vol. 139, No. 1, 2013, pp. 101–108.

19.

Zhou

, Zhao

, Peter

, and Jing

. Safety Effects of Median Treatments Using Longitudinal Channelizers: Empirical Bayesian Before-and-After Study. Journal of Transportation Engineering, Vol. 139, No. 12, 2013, pp. 1149–1155.

20.

Persaud

, and Lyon

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