The University of Tennessee, Knoxville


Tennessee Fights Roadway Departure Crashes

by Matt Cate, P.E.

The Federal Highway Administration (FHWA) defines a roadway departure crash as one "in which a vehicle crosses an edge line or a center line, or otherwise leaves the traveled way." If this sounds like a broad definition, it is. Roadway departure (RD) crashes encompass a variety of crash scenarios, including collisions between vehicles traveling in opposite directions on the same roadway, vehicles striking terrain and drainage features, and collisions with fixed objects such as trees and utility poles. These crashes represent a significant percentage of highway fatalities in the United States. With this in mind, a number of resources have been committed to the fight against RD. This article will highlight these resources at both the national and state levels and discuss several events and resources available through TTAP to help you combat RD crashes in your local community.

State and National Statistics

Nationally, RD was involved in 51% of the nation's 29,867 fatal crashes in 2011. Among these RD fatal crashes, 24% involved a vehicle leaving the right side of the roadway, 17% involved a vehicle crossing the roadway centerline or median, and 10% involved a vehicle leaving the left side of the roadway. Many of these crashes involve a collision with a fixed object adjacent to the roadway. Nationally, trees and traffic barriers combine to account for almost half of all fatal crashes where collision with a fixed object is listed as the first harmful event.

In Tennessee, RD is involved in an even-higher percentage of fatal crashes. In 2013, 623 of 995 roadway fatalities (63%) resulted from RD. Trees, ditches, and embankments accounted for more than half of the state's fixed object fatalities in 2012. The impact of RD crashes becomes even more evident when examining trends in serious injury crashes. While lane departure deaths have declined slightly since 2008, serious injuries resulting from lane departure crashes have increased from 2,480 in 2008 to 3,146 in 2012 (an increase of almost 27%).

Strategies to Prevent Roadway Departure Crashes In an effort to reduce the rate and overall occurrence of fatalities and injuries on our nation's roads, FHWA developed its Focused Approach to Safety. As a part of this program, FHWA has made RD one of three emphasis areas for which states may receive additional technical assistance, training, and data analysis. Tennessee is currently a RD focus state. FHWA also developed a Roadway Departure Strategic Plan (2013) to help guide its own activities and interactions with state DOTs. This 2013 plan establishes overturning crashes, opposite direction crashes, and roadside tree and shrub crashes as its primary points of emphasis.

FHWA has also supported the development and implementation of a number of countermeasures against RD. Included among these strategies are:

FWHA has included several of these treatments on its list of Proven Safety Countermeasures. Longitudinal rumble strips and stripes on two-lane roads, enhanced delineation and friction for horizontal curves, and the Safety Edge are RD countermeasures included on the current list.

Finally, FHWA is emphasizing systemic safety improvements as a way to proactively address a number of highway safety concerns, including RD. The systemic approach to safety allows state and local agencies to proactively apply safety treatments across the transportation network by assessing risk rather than reactively providing improvements after crashes occur. This flexibility is especially important given the seemingly random nature of many RD crashes.

The Tennessee Department of Transportation (TDOT) has also taken steps to address RD crashes on our state's roadways. The 2014 Tennessee Strategic Highway Safety Plan (SHSP) features RD prominently in its Infrastructure Improvements Emphasis Area Plan. In the period from 2008 to 2012, RD-related fatalities and serious injuries (44.5%) were by far the most prevalent crash type by infrastructure category, well ahead of intersections (26.1%), railroad crossings (0.1%), and other (29.2%).

The 2014 SHSP identifies several strategies to decrease the occurrence and severity of RD crashes over the next five years, including:

The plan also designates TTAP as an outlet for training and information specific to the Infrastructure Improvements Emphasis Area.

By including these emphasis areas and countermeasures in the SHSP, TDOT can use Highway Safety Improvement Program (HSIP) funds to implement improvements at locations where crash data or systemic risk analysis indicate a higher than average likelihood of crashes.

How Can TTAP Help You Address Roadway Departure Crashes?

As Tennessee's Local Technical Assistance Program (LTAP) center, one of TTAP's primary tasks is to provide training, technology transfer, and technical assistance resources that help local agencies to improve roadway safety. We want to take this opportunity to highlight several of these resources and to preview an upcoming event that will showcase one of the key RD countermeasures.


TTAP's training program includes a number of workshop titles that address roadway departure crashes by providing information on safety data analysis and countermeasures, roadway maintenance and design, and traffic operations. Each of these classes addresses one or more elements of the roadway that may affect the probability of RD crashes. Included in this list are:

Dates and locations are shown for classes scheduled in the remainder of 2015. Many of the other workshops will be offered again in 2016. All training titles are available upon request - please contact Frank Brewer, TTAP Training Coordinator, for additional information regarding this process.

Technical Assistance

TTAP provides free technical assistance to any local agency in Tennessee. The scope of this assistance can range from a single phone call or email to one or more on-site visits depending on the type and complexity of the issue being evaluated. TTAP's staff includes three engineers who are available to help you address a specific concern or condition at a real-world location. TTAP's technical assistance efforts typically focus on providing lowcost safety improvements such as signs, markings, and delineators to address safety issues.

TTAP's technical assistance program also incorporates an equipment loan program, including access to a Safety Edge show made available through FHWA (see sidebar). To learn more about TTAP's technical assistance program, visit our website at or contact Matt Cate at

Technology Transfer

Technology transfer, or T2, is the third and final area in which TTAP provides support to Tennessee's local transportation agencies. Our T2 program includes the RoadTalk newsletter, video and publication libraries, the TTAP website, and special events such as the August 2014 Safety Edge Open House and Demonstration. We constantly strive to bring you information on new safety technology and resources, as well as focusing on the tried and true techniques that any agency can use to improve safety on its roadways.

As Dr. Clarke mentions in his "From the Director" column, TTAP will increase its focus on special events and reference materials that have been developed or customized for our in-state audience of local officials. The next of these T2 events will be a High Friction Surface Treatments (HFST) Open House and Demonstration to be held in Nashville in September. Watch the TTAP website, your email inbox, and future issues of RoadTalk for more information on these special events and publications.

Roadway Departure Resources on the Web

Safety Edge Shoe Available for Use by Tennessee Local Agencies

If you attended the August 2014 Safety Edge Open House and Demonstration event co-hosted by TTAP, FHWA, and TDOT, you are already familiar with the basics of the Safety Edge, its benefits, and the equipment required to create it during paving projects. If not, please visit the TTAP website ( to see pictures, video, and materials from the event held in Nashville. You may also wish to visit FHWA's Safety Edge website ( to see research reports, national crash statistics, case studies, and more. Whether or not you attended the event in Nashville, TTAP has a Trans Tech Shoulder Wedge Maker ( available for use by any Tennessee city or county agency who wants to use the safety edge on new construction or resurfacing projects. To learn more about this opportunity or to request use of the device, please contact Matt Cate at 865-974-4614 or