Study Details

Study Title: Safety Performance Evaluation: Crash Modification Factor or Crash Modification Function?

Authors: Zhao et al.

Publication Date:JAN, 2017

Abstract: The treatment of shoulder rumble stripes, shoulder widening (from 0 to 2 feet) and pavement resurfacing (RSR) was deployed to more than 400 centerline miles of rural two-lane highways in Missouri. The safety performance of the RSR treatment was evaluated with the empirical Bayesian before and after study method based on the roadway characteristics and traffic and crash data collected. Crash modification factors (CMF) for 20 categories of crash severity and/or collision types were calculated. Generally, the RSR treatment effectively improves safety performance of rural two-lane roads, especially for fatal and injury crashes. Meanwhile, the RSR treatment is more effective for run-off road and head-on crashes than for total crashes. A cumulative residual (CURE) analysis reveals that fixed-value CMFs for all annual average daily traffics (AADT) range are likely to conclude with biased estimation on the RSR’s safety performance. The crash modification function (CMFunction) was introduced in this study, and a sample size of 16 was selected to develop the CMFunction based on the sensitivity analysis results. CMFunctions were developed for two collision types under different severity levels. The CURE plot indicates that CMFunctions produce unbiased crash frequency prediction results and, therefore, are more reliable than fixed-value CMFs.

Study Citation: Zhao, J., K. Kolody, C. Polk, J. Ritter, H. Brown, and C. Sun. "Safety Performance Evaluation: Crash Modification Factor or Crash Modification Function?". Presented at the 96th Annual Meeting of the Transportation Research Board, Paper No. 17-00046, Washington, D.C., (2017).

Related Citations: Zhao, J., C. Polk, J. Ritter, and K. Silverman. "Safety Performance of Shoulder Rumble Stripes on Rural Roadways". ITE Journal, March 2017, pp 44-48.


CMFs Associated With This Study

Category: Shoulder treatments

Countermeasure: Install a combination of shoulder rumble stripes, shoulder widening (from 0 to 2 ft) and resurface pavement

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
CMF EquationCRF Equation3 StarsAllNot specifiedRural
CMF EquationCRF Equation3 StarsAllA,B,CNot specifiedRural
CMF EquationCRF Equation3 StarsAllONot specifiedRural
CMF EquationCRF Equation3 StarsAllNot specifiedRural
CMF EquationCRF Equation3 StarsAllA,B,CNot specifiedRural
CMF EquationCRF Equation3 StarsAllA,B,C,ONot specifiedRural
CMF EquationCRF Equation3 StarsAllK,A,B,CNot specifiedRural
CMF EquationCRF Equation3 StarsAllA,B,C,ONot specifiedRural
CMF EquationCRF Equation3 StarsAllAllNot specifiedRural
CMF EquationCRF Equation3 StarsHead on,Run off roadNot specifiedRural
CMF EquationCRF Equation3 StarsHead on,Run off roadA,B,CNot specifiedRural
CMF EquationCRF Equation3 StarsHead on,Run off roadONot specifiedRural
CMF EquationCRF Equation3 StarsHead on,Run off roadNot specifiedRural
CMF EquationCRF Equation3 StarsHead on,Run off roadA,B,CNot specifiedRural
CMF EquationCRF Equation3 StarsHead on,Run off roadA,B,C,ONot specifiedRural
CMF EquationCRF Equation3 StarsHead on,Run off roadK,A,B,CNot specifiedRural
CMF EquationCRF Equation3 StarsHead on,Run off roadA,B,C,ONot specifiedRural
CMF EquationCRF Equation3 StarsHead on,Run off roadAllNot specifiedRural