Roadway Features

The design and features of roadways and intersections—such as the number and width of traffic lanes, turn lanes, shoulder types, median width, traffic control devices, pavement markings, roadside hardware, and traffic volumes—play a significant role in road safety. With Roadway Departure and Intersections as emphasis areas in Illinois' Strategic Highway Safety Plan (SHSP), opportunities to eliminate these types of severe crash through engineering safety analysis and roadway safety infrastructure improvements are pursued. The department has implemented strategies such as:

• Median Cable Rail. Median crossover crashes are a form of roadway departure crashes and occur when a motorist leaves the lane of travel, crosses the divided median, and hits an approaching vehicle head-on. The installation of median cable rail, a crash-tested roadside safety device, has proven to be highly effective in preventing these types of crashes.  See the attached video for more information.
• Centerline and Shoulder Rumble Strips/Rumble Stripes. Roadway departure crashes that are a result of distracted, fatigued, and impaired driving can be reduced with the installation of both milled-in centerline and shoulder rumble strips/rumble stripes. These strips alert drivers when they veer out of their lane through vibration and noise, helping reduce crashes, particularly those that involve crossing the roadway centerline.  To learn more, please navigate to the Rumble Strips and Rumble Stripes website.
• Chevrons and Advanced Warning Signs. Curves account for 10% of severe injury and fatal crashes in Illinois, with over 30% of roadway departure crashes occurring on curves. The installation of chevrons and advanced warning signs helps guide drivers through curves, significantly reducing the likelihood of accidents—especially at night. To learn more, please navigate to the Horizontal Curve Safety website.

Intersections are planned points of conflict on the roadway system. This includes U.S. and state highways, county roads, and local streets. Motorized and non-motorized users are crossing paths as they travel through or turn from one route to another. Intersections are a primary emphasis area in the SHSP, as they account for over 25% of severe injury and fatal crashes. Turning and angle crashes are the predominant type of severe crash occurring at intersections and the safety challenges vary depending on whether the intersection is signalized or unsignalized and whether it's located in an urban or rural area. A wide variety of safety infrastructure strategies include alternative geometric designs and traffic control devices.

• Flashing Yellow Arrows (FYA). Failure to yield to oncoming vehicles is a common cause of angle and turning crashes. The modification of traffic signals to include FYA provides more guidance to the motorist to allow for turning at an intersection while yielding to oncoming vehicles. The addition of FYA can improve the safety performance of an intersection by over 25 percent while maximizing the traffic flow through an intersection. See the attached video for more information.
• Roundabouts. Eliminating conflict points and reducing the vehicle speeds can significantly reduce severe crashes occurring at intersections. Roundabouts are an alternative geometric design that achieves this.

Crashes, and ultimately the severity of a crash, are a result of various factors, including the driver, vehicle type, and roadway characteristics. Roadway safety infrastructure improvements can impact driver behavior and the effects of a vehicle operating on the roadway to affect the overall frequency and severity of a crash.

Engineering safety analyses are used to identify high-risk areas and determine effective countermeasures. IDOT continually evaluates safety performance of a roadway and can implement roadway safety infrastructure improvements throughout the transportation management process.

These improvements are carried out in several ways, including simple in-house fixes, larger construction projects, or dedicated highway safety improvement initiatives. This allows IDOT to maximize its safety efforts across the entire public roadway system. Stand-alone infrastructure safety improvements are funded through the core federal program, the Highway Safety Improvement Program (HSIP), which is specifically focused on reducing fatality and serious injuries on all public roads. To learn more, please navigate to the Highway Safety Improvement Program webpage.

The department conducts Road Safety Audits (RSA), a formal safety performance review by a multi-discipline independent team. This occurs periodically on both state and local roadways to evaluate the safety performance of a roadway and identify low cost, easily implemented safety strategies ranging from infrastructure improvements to targeted enforcement efforts. More often, a less formal roadway safety review (RSR) is appropriate and can include the roadway owner on the review team. To learn more, please navigate to the Road Safety Audits webpage.