Study Details

Study Title: Development Of Crash Modification Factors For The Application Of The Safetyedge Treatment On Two-Lane Rural Roads

Authors: Donnell et al.

Publication Date:MAR, 2017

Abstract: This study estimated Crash Modification Factors (CMFs) for the SafetyEdgeSM paving technique on two-lane rural highways in Ohio, Iowa, and North Carolina. The SafetyEdgeSM provides a tapered roadway edge so that vehicles, on first incidence of experiencing a run-off-road event, can recover their trajectory more easily than more common pavement edges. The average angle of the SafetyEdgeSM was 31.8 degrees in Ohio, 29.7 degrees in Iowa, and 30.0 degrees in North Carolina. An empirical Bayes observational before-after evaluation found that the SafetyEdgeSM treatment was associated with statistically significant reductions in fatal and injury (FI), run-off-road (ROR), opposite direction (OPPDIR) including head-on and sideswipe, and drop-off-related crashes. A Crash Modification Function was calibrated to capture this relationship simultaneously with the variation of the CMF with other factors. An economic evaluation found that the SafetyEdgeSM paving technique is cost-effective, with the benefit-cost ratios ranging from 330 to 1,652 for ROR crashes, and from 409 to 2,044 for FI crashes. Finally, a pavement edge field data collection effort found that the reference group and SafetyEdgeSM treatment sites in North Carolina and Ohio often contained compacted backfill material, indicating traffic had not been exposed to the pavement edge, or shoulder maintenance had been performed recently. This is a good indication that the SafetyEdgeSM shape can hold backfill as well as the traditional shaped pavement edge. In Iowa, the field data collection effort showed that the backfill material was below the paved roadway surface, but the SafetyEdgeSM appeared to maintain its shape over time.

Study Citation: Donnell, E., C. Lyon, B. Persaud, F. Gross, and K. Eccles. "Development of Crash Modification Factors for the Application of the SafetyEdgeSM on Two-Lane Rural Roads". Federal Highway Administration, Washington, D.C. (March 2017).


CMFs Associated With This Study

Category: Shoulder treatments

Countermeasure: Install safety edge treatment

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.9178.34 StarsRun off roadAllPrincipal Arterial OtherRural
0.69230.85 StarsRun off roadAllPrincipal Arterial OtherRural
0.77422.65 StarsAllAllPrincipal Arterial OtherRural
0.9386.24 StarsAllAllPrincipal Arterial OtherRural
1.07-75 StarsAllAllPrincipal Arterial OtherRural
1.048-4.84 StarsAllAllPrincipal Arterial OtherRural
0.51148.95 StarsAllAllPrincipal Arterial OtherRural
0.9891.14 StarsAllAllPrincipal Arterial OtherRural
0.84215.84 StarsAllK,A,BPrincipal Arterial OtherRural
0.60239.84 StarsAllK,A,BPrincipal Arterial OtherRural
0.9861.44 StarsAllK,A,BPrincipal Arterial OtherRural
0.9722.84 StarsAllK,A,BPrincipal Arterial OtherRural
0.34365.74 StarsAllK,A,BPrincipal Arterial OtherRural
0.89210.85 StarsAllK,A,BPrincipal Arterial OtherRural
0.72427.64 StarsRun off roadAllPrincipal Arterial OtherRural
1.016-1.63 StarsRun off roadAllPrincipal Arterial OtherRural
0.9693.14 StarsRun off roadAllPrincipal Arterial OtherRural
0.76423.65 StarsRun off roadAllPrincipal Arterial OtherRural
0.11588.54 StarsRun off roadAllPrincipal Arterial OtherRural
0.79215 StarsRun off roadAllPrincipal Arterial OtherRural
0.68324 StarsHead onAllPrincipal Arterial OtherRural
0.45854.24 StarsHead onAllPrincipal Arterial OtherRural
0.75124.95 StarsHead onAllPrincipal Arterial OtherRural
1.172-17.24 StarsHead onAllPrincipal Arterial OtherRural
0.35564.54 StarsHead onAllPrincipal Arterial OtherRural
0.81318.75 StarsHead onAllPrincipal Arterial OtherRural
0.68131.94 StarsOtherAllPrincipal Arterial OtherRural
0.62837.25 StarsOtherAllPrincipal Arterial OtherRural
0.72627.44 StarsOtherAllPrincipal Arterial OtherRural
0.65534.55 StarsOtherAllPrincipal Arterial OtherRural
1.009-0.94 StarsRun off roadAllPrincipal Arterial OtherRural
0.65134.95 StarsRun off roadAllPrincipal Arterial OtherRural
0.9811.94 StarsRun off roadAllPrincipal Arterial OtherRural
0.77722.35 StarsRun off roadAllPrincipal Arterial OtherRural
0.86613.45 StarsRun off roadAllPrincipal Arterial OtherRural
0.76423.65 StarsRun off roadAllPrincipal Arterial OtherRural
0.88111.95 StarsRun off roadAllPrincipal Arterial OtherRural
0.64335.75 StarsRun off roadAllPrincipal Arterial OtherRural
0.75924.15 StarsRun off roadAllPrincipal Arterial OtherRural
0.83616.45 StarsRun off roadAllPrincipal Arterial OtherRural
0.81818.25 StarsRun off roadAllPrincipal Arterial OtherRural
0.69530.55 StarsRun off roadAllPrincipal Arterial OtherRural