ATSSA: Improving Driver Behavior with Infrastructure Safety Countermeasures

4 Improving Driver Behavior with Infrastructure Safety Countermeasures Part I: Alerting Drivers by Providing Information CASE 1: Centerline, Shoulder, and Transverse Rumble Strips R oadway departure is one of the more severe types of crashes, compared with other crash types. Roadway departure occurs when a vehicle departs from the roadway by either crossing an edge line or a centerline. The latter may result in a head-on collision. The reasons for roadway-departure events are varied but do include the driver attempting to avoid a vehicle, an object, or an animal in the travel lane; inattentive driving due to distraction, fatigue, medical conditions, or the use of alcohol or drugs; wet or slippery pavement conditions; driver inexperience; or traveling too fast through curves or downhill. In difficult situations, many drivers do not have the knowledge or the skills to maintain or regain control of the vehicle in a safe manner. Although features of the roadway infrastructure cannot affect the initial driver behavior that leads to the roadway departure, they can change the sequence of crash events and prevent or reduce the severity of those crashes. To effectively address roadway-departure crashes, it is critical to select the appropriate set of roadway safety features and install them correctly in the locations with the greatest potential to prevent or reduce the severity of crashes. Many of the roadway safety features that can prevent crashes are low-cost, are easy to install, and can be implemented systemically throughout the jurisdiction’s roadway network. One example of a low-cost infrastructure treatment is centerline or shoulder rumble strips. The vibration and noise caused by these grooves in the pavement can greatly influence drivers’ reactions to crossing the edge or centerline by prompting a corrective action when alerted that they are leaving the roadway. The vibration and noise can also awaken a drowsy driver. Additionally, rumble strips can serve as an effective guide, alerting drivers as to the location of the travel lane when fog, snow, driving rain, or darkness obscures pavement markings. Figure 2. Shoulder rumble strip on Interstate 95 (North), Stafford County, Va. (Image: James Scott Baron, ATSSA) The results of an evaluation of shoulder rumble strips, which included more than 200 sites in 19 states, indicate a reduction in single-vehicle roadway-departure collisions of 11 percent to 18 percent for urban and rural freeways and 15 percent for two-lane rural roads. Furthermore, M any features of the roadway’s infrastructure can prevent driver errors and help reduce the potential for crashes. These features can warn drivers of an upcoming change in the driving environment that requires action or alerts drivers to an error before the event results in a crash. Most of these elements are low-cost, are easy to install, and can be implemented systemically throughout the jurisdiction’s roadway network. The following five case studies provide examples of safer infrastructure used to alert drivers so they may bring the vehicle back on course, reducing the likelihood of a crash. Figure 3. A sample of milled centerline rumble strips (Image: Neal Hawkins, Center for Transportation Research)