Study Details

Study Title: Safety Effectiveness of Various Types of Shoulders on Rural Two-Lane Roads in Winter and Non-Winter Periods

Authors: Zeng and Schrock

Publication Date: JAN, 2013

Abstract: There has been growing recognition of the quantitative effects of various roadway designs and traffic control strategies on safety. Meanwhile, there is increasing interest in measuring the variances of safety effectiveness in different periods of the year for similar roadway designs or similar traffic control strategies. This study tried to address the variances of safety effectiveness between the winter and non-winter periods for the ten most common shoulder designs in Kansas. Traffic and geometric data were collected on 6,510 miles (10,477 km) of rural two-lane highways in Kansas. A cross-sectional approach was applied to develop winter period safety performance functions (SPFs), non-winter period SPFs and SPFs aggregated at an annual level in which shoulder designs were treated as independent variables. A variance test was conducted based on these SPFs to investigate the variances of safety effectiveness between the two different periods. It was found that wider and upgraded shoulders offer significant less safety benefit in reducing total crash number during winter periods than during non-winter periods. The indexes of safety effectiveness for the winter period are larger than those for the non-winter period by between 13 to 25 percent. However, winter weather appears not to significantly diminish wider and/or upgraded shoulders' safety benefit in reducing crash severity and the number of shoulder related crashes. The results demonstrate that treating the winter and non-winter data equally is likely to bias a shoulder's estimated safety effectiveness in total crashes.

Study Citation: Zeng, H., and S. D. Schrock, "Safety Effectiveness of Various Types of Shoulders on Rural Two-Lane Roads in Winter and Non-Winter Periods," Transportation Research Board 92nd Annual Meeting Compendium of Papers, Washington, DC, (2013).


CMFs Associated With This Study

Category: Shoulder treatments

Countermeasure: Convert a 2 ft. turf shoulder to a 10 ft. composite shoulder (first 3 ft. bituminous with remainder aggregate)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.66343 StarsAllK,A,B,CNot specifiedRural
0.47533 StarsOtherAllNot specifiedRural
1.06-63 StarsAllAllNot specifiedRural
0.85153 StarsAllAllNot specifiedRural
0.9643 StarsAllAllNot specifiedRural
0.61393 StarsAllK,A,B,CNot specifiedRural
0.63373 StarsAllK,A,B,CNot specifiedRural
0.5503 StarsOtherAllNot specifiedRural
0.45553 StarsOtherAllNot specifiedRural

Countermeasure: Convert a 2 ft. turf shoulder to a 10 ft. composite shoulder (first 3 ft. bituminous with remainder turf)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.01-13 StarsAllAllNot specifiedRural
0.88123 StarsAllAllNot specifiedRural
0.9553 StarsAllAllNot specifiedRural
0.48523 StarsAllK,A,B,CNot specifiedRural
0.59413 StarsAllK,A,B,CNot specifiedRural
0.53473 StarsAllK,A,B,CNot specifiedRural
0.41593 StarsOtherAllNot specifiedRural
0.43573 StarsOtherAllNot specifiedRural
0.42583 StarsOtherAllNot specifiedRural

Countermeasure: Convert a 2 ft. turf shoulder to a 10 ft. paved shoulder (bituminous base)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.74263 StarsAllAllNot specifiedRural
0.42583 StarsAllK,A,B,CNot specifiedRural
0.44563 StarsAllK,A,B,CNot specifiedRural
0.4603 StarsOtherAllNot specifiedRural
0.4603 StarsOtherAllNot specifiedRural
0.84163 StarsAllAllNot specifiedRural
0.79213 StarsAllAllNot specifiedRural
0.46543 StarsAllK,A,B,CNot specifiedRural
0.4603 StarsOtherAllNot specifiedRural

Countermeasure: Convert a 2 ft. turf shoulder to a 10 ft. paved shoulder (Portland cement concrete)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.55453 StarsOtherAllNot specifiedRural
0.52483 StarsOtherAllNot specifiedRural
0.53473 StarsAllK,A,B,CNot specifiedRural
0.83173 StarsAllAllNot specifiedRural
0.67333 StarsAllAllNot specifiedRural
0.76243 StarsAllAllNot specifiedRural
0.6403 StarsAllK,A,B,CNot specifiedRural
0.48523 StarsAllK,A,B,CNot specifiedRural
0.52483 StarsOtherAllNot specifiedRural

Countermeasure: Convert a 2 ft. turf shoulder to a 3 ft. turf shoulder

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.82183 StarsOtherAllNot specifiedRural
0.9643 StarsAllAllNot specifiedRural
0.9553 StarsAllAllNot specifiedRural
0.9643 StarsAllAllNot specifiedRural
0.9463 StarsAllK,A,B,CNot specifiedRural
0.9823 StarsAllK,A,B,CNot specifiedRural
0.9643 StarsAllK,A,B,CNot specifiedRural
0.74263 StarsOtherAllNot specifiedRural
0.9193 StarsOtherAllNot specifiedRural

Countermeasure: Convert a 2 ft. turf shoulder to a 4 ft. turf shoulder

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
103 StarsAllAllNot specifiedRural
0.9373 StarsAllAllNot specifiedRural
0.9733 StarsAllAllNot specifiedRural
0.67333 StarsAllK,A,B,CNot specifiedRural
0.79213 StarsAllK,A,B,CNot specifiedRural
0.72283 StarsAllK,A,B,CNot specifiedRural
0.76243 StarsOtherAllNot specifiedRural
0.79213 StarsOtherAllNot specifiedRural
0.77233 StarsOtherAllNot specifiedRural

Countermeasure: Convert a 2 ft. turf shoulder to a 6 ft. composite shoulder (first 3 ft. bituminous with remainder turf)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.8203 StarsAllAllNot specifiedRural
0.88123 StarsAllAllNot specifiedRural
0.83173 StarsAllAllNot specifiedRural
0.58423 StarsAllK,A,B,CNot specifiedRural
0.58423 StarsAllK,A,B,CNot specifiedRural
0.58423 StarsAllK,A,B,CNot specifiedRural
0.69313 StarsOtherAllNot specifiedRural
0.44563 StarsOtherAllNot specifiedRural
0.58423 StarsOtherAllNot specifiedRural

Countermeasure: Convert a 2 ft. turf shoulder to a 6 ft. turf shoulder

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.59413 StarsOtherAllNot specifiedRural
0.59413 StarsOtherAllNot specifiedRural
0.9553 StarsAllAllNot specifiedRural
0.81193 StarsAllAllNot specifiedRural
0.89113 StarsAllAllNot specifiedRural
0.58423 StarsAllK,A,B,CNot specifiedRural
0.71293 StarsAllK,A,B,CNot specifiedRural
0.64363 StarsAllK,A,B,CNot specifiedRural
0.59413 StarsOtherAllNot specifiedRural

Countermeasure: Convert a 2 ft. turf shoulder to an 8 ft. composite shoulder (first 3 ft. bituminous with remainder turf)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.52483 StarsOtherAllNot specifiedRural
0.56443 StarsOtherAllNot specifiedRural
103 StarsAllAllNot specifiedRural
0.85153 StarsAllAllNot specifiedRural
0.9373 StarsAllAllNot specifiedRural
0.65353 StarsAllK,A,B,CNot specifiedRural
0.56443 StarsAllK,A,B,CNot specifiedRural
0.61393 StarsAllK,A,B,CNot specifiedRural
0.5503 StarsOtherAllNot specifiedRural