Researchers
Tom McDonald
Robert Sperry
About the research
The Institute for Transportation (InTrans) at Iowa State University initially completed work on an in-depth study of crash history on low-volume, rural roads in Iowa in December 2010. Results indicated that unpaved roads with traffic volumes greater than 100 vehicles per day (vpd) exhibit significantly higher crash frequencies, rates, and densities than any other class of low-volume road examined, paved or unpaved.
The total mileage for this class of roadway in Iowa is only about 4,400 miles, spread over 99 counties in the state, so it’s certainly a manageable number of miles for individual rural agencies.
The purpose of this study was to identify and examine several unpaved, local road segments with higher than average crash frequencies, select and undertake potentially-beneficial mitigation, and evaluate the results as time allowed. A variety of low-cost options were considered, including engineering improvements, enhanced efforts by law enforcement, and educational initiatives.
Using input, active support, and participation from local agencies and state and Federal safety advocates, the study afforded a unique opportunity to examine useful tools for local rural agencies to utilize in addressing safety on this particular type of roadway.
Project Details
TR-630, 11-393
01/01/11
10/30/13
Federal Highway Adminisitration Accelerating Safety Activities Program
Iowa Department of Transportation
Iowa Highway Research Board
Midwest Transportation Consortium
U.S. DOT RITA
Researchers
Neal Hawkins
hawkins@iastate.edu email >Director Research Administration, ISU
About the research
The main goal of this research is to provide agencies with tools they can use in designing transition zones from high-speed rural roadways into to low-speed communities.
Funding Sources:
Federal Highway Adminisitration Accelerating Safety Activities Program
Iowa Department of Transportation
Iowa Highway Research Board
Midwest Transportation Consortium
U.S. DOT RITA
Researchers
Robert Sperry
Tom McDonald
About the research
Roadway departure crashes are a serious traffic safety concern. These crashes account for about 53 percent of US highway fatalities and one million injuries annually. The Iowa Department of Transportation (DOT) estimates approximately 52 percent of roadway-related fatal crashes in Iowa are lane departures. The Federal Highway Administration (FHWA) estimated in 2010 that 160 fatalities and more than 11,000 injuries related to unsafe pavement edges occur annually.
The Safety Edge is a design feature that creates a 30 degree fillet along the outside edge of a roadway during paving operations. The FHWA developed the Safety Edge based on research that indicated a sloped pavement edge surface could be traversed more easily by vehicles attempting to remount the pavement after leaving the paved roadway surface.
In this Phase II study, researchers observed and documented advances in design and utilization of Safety Edge equipment, sampled, tested, and assessed consolidation of the Safety Edge, inspected field conditions on previously-installed Safety Edge projects, evaluated changes in shoulder settlement/erosion, and assessed any deterioration of sloped HMA pavement edges.
Based on observations and measurements, the research team concluded that, even considering that not all results were consistent and didn’t meet the “ideal” 30 degree slope angle, almost all Safety Edge slopes included in this evaluation project resulted in more durable and passable slopes than what would be expected with conventional pavement edges.
This Phase II report and tech brief document the evaluation of Safety Edge projects and results in Iowa and include an array of conclusions and practical recommendations.
