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 |  | 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 | | 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 | | 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 | | 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 | | 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 | | 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 | | 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 | | All | All | All | Not specified |
| 1.17 | -17 | | 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 | | All | All | All | Not specified |
| 0.95 | 5 | | 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 | | All | All | All | Not specified |
| 0.9 | 10 | | 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 | | All | All | All | Not specified |
| 0.85 | 15 | | 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 | | All | All | All | Not specified |
| 0.81 | 19 | | 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 | | All | All | All | Not specified |
| 0.77 | 23 | | Single vehicle | All | All | Not specified |
