Study Details

Study Title: Development of Crash Modification Factors for Combined Treatments on Rural Two-lane Roads

Authors: CH2M Hill

Publication Date:AUG, 2015

Abstract: More than half (57 percent) of U.S. traffic fatalities occur after a driver crosses the edge or centerline of a roadway, among which two-thirds occur in rural areas (FHWA, 2015). Rumble strips (and rumble stripes) have been proven to be an effective means of reducing run-off-the-road crashes. They are primarily used to warn drivers when they have drifted from their lane. Wide paved shoulders and high friction surface treatment are also effective countermeasures for deterring run-off-the-road crashes. In order to improve upon the safety performance of rural two-lane highways, the Missouri Department of Transportation (MoDOT) has deployed a combined treatment of shoulder rumble stripes, shoulder widening from no shoulder to 2 foot shoulder width and pavement resurfacing (combined RS-SW-PR treatment) to over 400 centerline miles of roadway segments within its jurisdiction. In an effort to objectively evaluate the safety performance of the treatment, MoDOT contracted with CH2M HILL to calculate the crash modification factors (CMFs) for the combined RS-SW-PR treatment for multiple designated crash severity levels and collision types. The safety benefits for individual treatments of shoulder rumble stripes, shoulder widening, and pavement resurfacing have been documented in previous studies. However, no CMFs have been reported yet for the safety benefits these treatments in combination. Furthermore, it is not applicable to estimate the CMFs for the combined RS-SW-PR treatment by multiplying the CMFs for all individual treatments together directly since it is likely to result in an overestimation of the safety benefits.

Study Citation: CH2M Hill. "Development of Crash Modification Factors for Combined Treatments on Rural Two-lane Roads." Missouri Department of Transportation. (August 2015).


CMFs Associated With This Study

Category: Shoulder treatments

Countermeasure: Install shoulder rumble stripe, widen shoulder from 0 to 2 feet, and pavement resurfacing

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.54745.33 StarsAllKNot specifiedRural
0.88211.83 StarsAllANot specifiedRural
0.75624.43 StarsAllB,CNot specifiedRural
0.9841.63 StarsAllONot specifiedRural
0.82217.83 StarsAllK,ANot specifiedRural
0.8203 StarsAllA,B,CNot specifiedRural
0.9277.33 StarsAllB,C,ONot specifiedRural
0.78421.63 StarsAllK,A,B,CNot specifiedRural
0.9373 StarsAllA,B,C,ONot specifiedRural
0.9188.23 StarsAllAllNot specifiedRural
0.55453 StarsHead on,Run off roadKNot specifiedRural
0.74925.13 StarsHead on,Run off roadANot specifiedRural
0.73226.83 StarsHead on,Run off roadB,CNot specifiedRural
1.01-13 StarsHead on,Run off roadONot specifiedRural
0.71293 StarsHead on,Run off roadK,ANot specifiedRural
0.74325.73 StarsHead on,Run off roadA,B,CNot specifiedRural
0.9089.23 StarsHead on,Run off roadB,C,ONot specifiedRural
0.72927.13 StarsHead on,Run off roadK,A,B,CNot specifiedRural
0.89110.93 StarsHead on,Run off roadA,B,C,ONot specifiedRural
0.87712.33 StarsHead on,Run off roadAllNot specifiedRural