Evaluation of Dynamic Speed Feedback Signs on Curves: A National Demonstration Project
Lane departure crashes are a significant safety concern. The majority of lane departure crashes occur on rural two-lane roadways, with a disproportionate number of these crashes on horizontal curves. Curve-related crashes involve a number of roadway and driver causative factors. A primary driver factor is speeding. Dynamic speed feedback sign (DSFS) systems are one method to reduce vehicle speeds and, consequently, crashes on curves. These systems show promise but they have not been fully evaluated on curves. The Center for Transportation Research and Education at Iowa State University conducted a national demonstration project to evaluate the effectiveness of two different DSFSs in reducing speed and crashes on curves at 22 total sites on rural two-lane roadways in seven States. The goal is to provide traffic safety engineers and other professionals with additional tools to manage speeds and crashes on rural horizontal curves more effectively. Data were collected before and at 1, 12, and 24 months after installation of the DSFS. On average, most sites had decreases in mean speeds, with decreases up to 10.9 miles per hour (mph) noted for both the point of curvature (PC) and center of curve (CC). Most sites experienced changes in 85th percentile speed of 3 mph or more at the PC, with the majority of sites having a decrease of 2 mph at the CC. The numbers of vehicles traveling 5, 10, 15, or 20 mph over the posted or advisory speed limit were also compared. Large reductions in the number of vehicles traveling over the posted or advisory speed occurred for all of the after periods at the PC and CC, indicating that the signs were effective in reducing high-end speeds, as well as average and 85th percentile speeds. A before-and-after crash analysis was also conducted, and crash modification factors (CMF) were developed. CMFs ranged from 0.93 to 0.95 depending on the crash type and direction of the crash.
- Record URL:
- Record URL:
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Corporate Authors:
Center for Transportation Research and Education
2711 South Loop Drive, Suite 4700
Ames, IA United States 50010-8664Federal Highway Administration
Office of Infrastrucutre R&D HRDI-12
Turner Fairbank Highway Research Center, 6300 Georgetown Pike
McLean, VA United States 22101-2296Iowa Department of Transportation
Iowa Highway Research Board, 800 Lincoln Way
Ames, IA United States 50010Midwest Transportation Consortium
Iowa State University, 2711 South Loop Drive, Suite 4700
Ames, IA United States 50010-8664Texas Department of Transportation
125 E. 11th Street
Austin, TX United States 78701-2483 -
Authors:
- Hallmark, Shauna L
- Hawkins, Neal
- Smadi, Omar
- Publication Date: 2015-1
Language
- English
Media Info
- Media Type: Digital/other
- Edition: Final Report
- Features: Appendices; Figures; Maps; Photos; References; Tables;
- Pagination: 210p
Subject/Index Terms
- TRT Terms: 85th percentile speed; Before and after studies; Crash analysis; Demonstration projects; Evaluation; Highway curves; Rural highways; Speed control; Speed signs
- Subject Areas: Highways; Operations and Traffic Management; Safety and Human Factors; I73: Traffic Control; I83: Accidents and the Human Factor;
Filing Info
- Accession Number: 01554383
- Record Type: Publication
- Report/Paper Numbers: FHWA-HRT-14-020, InTrans Project 08-320
- Contract Numbers: DTFH61-07-H-00022
- Files: NTL, TRIS, ATRI, USDOT, STATEDOT
- Created Date: Feb 26 2015 9:49AM