Study Details

Study Title: A Before-After Evaluation of the Realignment of Horizontal Curves on Rural Two-Lane Roads

Authors: Srinivasan et al.

Publication Date:JAN, 2018

Abstract: This study determined the crash modification factors (CMFs) associated with horizontal curve realignment using the before-after empirical Bayes method and compared the results from published CMFs from cross-sectional studies. This evaluation used data from rural, two-lane roads in California, North Carolina, and Ohio. The evaluation revealed a 68-percent reduction in total crashes, a 74-percent reduction in injury and fatal crashes, a 78-percent reduction in run-off-road and fixed object crashes, a 42-percent reduction in crashes during dark conditions, and an 80-percent reduction in wet-road crashes, all of which were statistically significant at the 95 percent confidence level. The results pertain to a range of site characteristics, the most important of which is the range of before and after degree of curve. The average degrees of curve in the before and after periods were 18.1 (with a minimum of 3.2 and a maximum of 52.1) and 6.9 (with a minimum of 0.0 and a maximum of 16.3), respectively. The average central angle of the curves was approximately 42 degrees (with a minimum of 1 and a maximum of 117). The CMFs from this before-after evaluation are lower compared to CMFs estimated from two previous cross-sectional studies. There is a need for further research with a larger sample of sites to assess the reliability of the CMFs obtained from this before-after evaluation.

Study Citation: Srinivasan, R., D. Carter., C. Lyon., and M. Albee. "A Before-After Evaluation of the Realignment of Horizontal Curves on Rural Two-Lane Roads". Presented at the 97th Annual Meeting of the Transportation Research Board, Paper No. 08-01803, Washington, D.C., (2018).


CMFs Associated With This Study

Category: Alignment

Countermeasure: Flatten horizontal curve

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.31568.54 StarsAllAllAllRural
0.25974.14 StarsAllK,A,B,CAllRural
0.21678.44 StarsFixed object,Run off roadAllAllRural
0.58441.64 StarsOtherAllAllRural
0.20479.64 StarsWet roadAllAllRural
CMF Equation1 StarAllAllAllRural