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(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.91 9 4 Stars Multiple vehicle All All Not specified

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

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.83 17 4 Stars Multiple vehicle All All Not specified

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

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.75 25 4 Stars Multiple vehicle All All Not specified

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

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.68 32 4 Stars Multiple vehicle All All Not specified

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

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.62 38 4 Stars Multiple vehicle All All Not specified

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

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.57 43 4 Stars Multiple vehicle All All Not specified

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

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.51 49 4 Stars Multiple vehicle All All Not specified

Category:Shoulder treatments

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

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.22 -22 4 Stars All All All Not specified
1.17 -17 4 Stars Single vehicle All All Not specified

Countermeasure: Widen paved shoulder from 3 ft to 4 ft

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.94 6 4 Stars All All All Not specified
0.95 5 4 Stars Single vehicle All All Not specified

Countermeasure: Widen paved shoulder from 3 ft to 5 ft

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.87 13 4 Stars All All All Not specified
0.9 10 4 Stars Single vehicle All All Not specified

Countermeasure: Widen paved shoulder from 3 ft to 6 ft

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.82 18 4 Stars All All All Not specified
0.85 15 4 Stars Single vehicle All All Not specified

Countermeasure: Widen paved shoulder from 3 ft to 7 ft

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.76 24 4 Stars All All All Not specified
0.81 19 4 Stars Single vehicle All All Not specified

Countermeasure: Widen paved shoulder from 3 ft to 8 ft

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.71 29 4 Stars All All All Not specified
0.77 23 4 Stars Single vehicle All All Not specified