Study Details
Study Title: Empirical Bayes Before-After Study on Safety Effect of Narrow Pavement Widening Projects in Texas
Authors: Wu et al.
Publication Date: 2015
Abstract: Texas has approximately 40,000 lane miles (64,000 km) of two-lane farm-to-market (FM) and 2 ranch-to-market (RM) roads with total paved widths of 18 to 22 ft (5.5 to 6.7 m), most of which 3 are in rural areas. Narrow pavement widening in Texas typically involves adding a total of 1- to 4 9-ft (0.3- to 2.4-m) lane width and/or a narrow shoulder to each direction of a narrow FM/RM 5 road. The main reasons for roadway widening are usually to improve safety, increase structural 6 capacity, and/or enhance pavement performance. The goal of this study is to investigate the 7 safety effects of narrow pavement widening projects for rural two-lane FM/RM roads in Texas. 8 A before-after comparison study was conducted using the empirical Bayes method to evaluate 9 how wider lanes/shoulders impact crash occurrence by type and severity. Of the 22 studied 10 projects, analysis showed a 31.5 percent reduction in total crashes; a 35.7 percent in run-off-the-11 road crashes; and a 55.4 percent reduction in head-on crashes after narrow widening projects 12 were constructed. The projects were also effective in reducing fatal crashes and injuries by about 13 29.5 percent. These findings suggest that narrow pavement widening is an effective safety 14 countermeasure on narrow two-lane FM/RM roads in rural areas.
Study Citation: Wu, H., Z. Han, M. Murphy, and Z. Zhang. "Before-After Study on Safety Effect of Narrow Pavement Widening Projects in Texas". Presented at the 94th Annual Meeting of the Transportation Research Board, Paper No. 15-3001, Washington, D.C., (2015).
CMFs Associated With This Study
Category: Roadway
Countermeasure: Widen Narrow Pavement
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.685 | 31.5 |  | All | All | Not specified | Rural |
| 0.643 | 35.7 | | Run off road | All | Not specified | Rural |
| 0.446 | 55.4 |  | Head on | All | Not specified | Rural |
| 0.705 | 29.5 | | All | K,A,B,C | Not specified | Rural |
| 0.693 | 30.7 | | All | A,B,C | Not specified | Rural |
| 0.683 | 31.7 | | All | O | Not specified | Rural |
