Study Details

Study Title: NCHRP Report 633: Impact of Shoulder Width and Median Width on Safety

Authors: Stamatiadis et al.

Publication Date: 2009

Abstract: This report contains the findings of research performed to quantify the safety and operational impacts of design element trade-offs and their associated risks. The report details the research performed and includes specific recommended crash prediction models and Accident Modification Factors (AMFs) for shoulder width and median width on rural four-lane roads. Thus, the report will be of immediate interest to engineers in state highway agencies responsible for geometric design and traffic operations and safety.

Study Citation: Stamatiadis, N., Pigman, J., Sacksteder, J, Ruff, W., and Lord, D. "Impact of Shoulder Width and Median Width on Safety". NCHRP Report 633. Transportation Research Board, Washington D.C., (2009).

Study Report: Download the Study Report Document


CMFs Associated With This Study

Category: Access management

Countermeasure: 10-ft to 20-ft conversion (median width)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.9193 StarsMultiple vehicleAllAllNot specified

Countermeasure: 10-ft to 30-ft conversion (median width)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.83173 StarsMultiple vehicleAllAllNot specified

Countermeasure: 10-ft to 40-ft converstion (median width)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.75253 StarsMultiple vehicleAllAllNot specified

Countermeasure: 10-ft to 50-ft conversion (median width)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.68323 StarsMultiple vehicleAllAllNot specified

Countermeasure: 10-ft to 60-ft conversion (median width)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.62383 StarsMultiple vehicleAllAllNot specified

Countermeasure: 10-ft to 70-ft conversion (median width)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.57433 StarsMultiple vehicleAllAllNot specified

Countermeasure: 10-ft to 80-ft conversion (median width)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.51493 StarsMultiple vehicleAllAllNot specified

Category:Shoulder treatments

Countermeasure: Reduce paved shoulder width from 3 ft to 0 ft

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.22-223 StarsAllAllAllNot specified
1.17-173 StarsSingle vehicleAllAllNot specified

Countermeasure: Widen paved shoulder from 3 ft to 4 ft

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.9463 StarsAllAllAllNot specified
0.9553 StarsSingle vehicleAllAllNot specified

Countermeasure: Widen paved shoulder from 3 ft to 5 ft

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.87133 StarsAllAllAllNot specified
0.9103 StarsSingle vehicleAllAllNot specified

Countermeasure: Widen paved shoulder from 3 ft to 6 ft

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.82183 StarsAllAllAllNot specified
0.85153 StarsSingle vehicleAllAllNot specified

Countermeasure: Widen paved shoulder from 3 ft to 7 ft

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.76243 StarsAllAllAllNot specified
0.81193 StarsSingle vehicleAllAllNot specified

Countermeasure: Widen paved shoulder from 3 ft to 8 ft

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.71293 StarsAllAllAllNot specified
0.77233 StarsSingle vehicleAllAllNot specified