A W-beam guardrail is often used to protect motorists from steep roadside slopes adjacent to high-speed roadways. Although previously designed systems have demonstrated acceptable safety performance, the long posts and half-post spacing have proven to be costly and introduce maintenance challenges. Using longer posts is more economical to users than having a system with posts installed at half-post spacing. Furthermore, the improved redirective capacity of the Midwest Guardrail System (MGS) provides the opportunity to eliminate the need for half-post spacing and thereby greatly reduces the cost of placing a barrier at the slope break point. A stiffened version of the MGS was developed for use adjacent to steep roadside slopes. The new design incorporates 2,743-mm (9-ft) long posts with 1,905-mm (75-in.) spacing. With the top of the W-beam mounted at a height of 787 mm (31 in.), this guardrail was successfully crash tested according to the currently proposed NCHRP Report 350 Update safety performance evaluation criteria. Hence, the stiffened MGS guardrail design with full post spacing is acceptable for use on the National Highway System. This new guardrail design will provide a safe and economical alternative for use along highways with steep slopes very close to the travelway.
Safety performance evaluation of cable median barriers on freeways in Florida