ATSSA: Improving Driver Behavior with Infrastructure Safety Countermeasures

18 Improving Driver Behavior with Infrastructure Safety Countermeasures A Safety countermeasure that significantly reduces crash severity is cable median barrier. When installed correctly in between opposing directions of traffic, the cable median barrier can redirect a vehicle back toward the intended travel lane to help prevent deadly head-on collisions. A collision still occurs between the errant vehicle and the cable barrier, but the outcome is likely to result in property damage only and not an injury or fatality as a result of a head-on collision. Also, cable median barrier can prevent a vehicle from traveling across the oncoming lanes and striking fixed objects alongside the roadway. Several state departments of transportation (including Illinois, Minnesota, and Missouri) determined there was an elimination of cross-median crashes and a reduction in the severity of roadway-departure crashes due to the installation of cable median barrier along several of their state highways. Cable barriers are often times used in the median where there is space to accommodate these devices. Often times, site conditions will require a semi-rigid post and beam guardrail system such as the MASH tested W-Beam. W-Beam barriers have been successfully used since the Interstate System was built in the 1950’s. With slight modifications, modern-day W-Beam is versatile enough to remain crashworthy with the higher center-of-gravity passenger vehicles seen on America’s roadways today. Part III: Minimizing Consequences When a Vehicle Leaves the Road CASE 12: Cable Median Barriers, Guardrails, and Crash Cushions A ccording to the FHWA and as reported in the Fatality Analysis Reporting System (FARS) database, approximately 57 percent of motor vehicle traffic fatalities that have occurred annually in the United States in recent years are due to roadway departure. The probability for roadway-departure crashes to have severe outcomes depends on side slopes, fixed-object density, offset to fixed objects, and shoulder width. Collision with a fixed object is usually identified as the first harmful event in run- off-road crashes. After a vehicle leaves the roadway, roadway safety improvements, such as those defined in this booklet, can help prevent or reduce the severity of a collision. Several options provide the ability to enhance safety by minimizing the consequences of a driver action that causes a vehicle to depart the roadway. Figure 31. Installed cable median barrier (Image: Gibraltar) Figure 32. A low-speed crash into a cable barrier system yielded a textbook vehicle capture (Image: Gibraltar)