Study Details
Study Title: Development of Crash Reduction Factors
Authors: Hovey and Chowdhury
Publication Date: 2005
Abstract: Crash reduction factors are used to identify and prioritize the most effective safety improvement measures, and prioritize and allocate available resources optimally for a highway safety improvement project. Simple before-and after analysis does account for the regression-to-the-mean bias. This research employs an Empirical Bayes (EB) methodology that overcomes the regression-to-the-mean property that is encountered in traditional before-and after analysis. Traffic, geometric and crash data for both the treatment and comparison sites were collected from Ohio in developing the crash reduction factors. Using data collected from Ohio, the EB methodology was applied in developing crash reduction factors for the following improvement categories: add a two-way left turn lane, install a median barrier, flatten slope and remove guardrail, remove or relocate a fixed object, flatten vertical curve, providing highway lighting and close median opening.
Study Citation: Hovey, P. W. and Chowdhury, M., "Development of Crash Reduction Factors." 14801(0), Ohio Department of Transportation, (2005)
Study Report: Download the Study Report Document
CMFs Associated With This Study
Category: Alignment
Countermeasure: Flatten crest vertical curve
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.8 | 20 |  | All | All | All | All |
| 0.49 | 51 | | All | K,A,B,C | All | All |
Category:Highway lighting
Countermeasure: Install lighting at interchanges
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.5 | 50 | | All | All | All | All |
| 0.74 | 26 | | All | K,A,B,C | All | All |
Category:Roadside
Countermeasure: Flatten side slopes and remove guardrail
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.58 | 42 | | All | All | All | All |
Countermeasure: Install median barrier
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.14 | 86 | | All | All | All | All |
| 0.12 | 88 | | All | K,A,B,C | All | All |
Countermeasure: Remove or relocate fixed objects outside of clear zone
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.62 | 38 | | All | All | All | All |
| 0.62 | 38 | | All | K,A,B,C | All | All |
Category:Roadway
Countermeasure: Add two-way left-turn lane
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.92 | 8 | | All | All | All |
| 0.8 | 20 | | All | K,A,B,C | All |
