Mid-America Transportation Center


Date of this Version


Document Type



MwRSF Research Report No. TRP-03-88-99


A 7.62-m long span guardrail system was developed for use over low-fill culverts. The long span design was constructed with two 2.66-mm (12-gauge) thick nested W-beam rails totaling 30.48 m in length. The nested W-beam rail was supported by sixteen W150x13.5 steel posts and six standard CRT posts, each with two 150x200x360 wood blockouts. Each post measured 1,830-mm long. Post spacings were 1,905-mm on center except for the 7.62-m spacing between the two CRT posts surrounding the unsupported span.

The research study included full-scale vehicle crash testing, using a 3⁄4-ton pickup truck. The test, impacting at a speed of 102.9 km/hr and an angle of 24.7 degrees, was conducted and reported in accordance with the requirements specified in NCHRP Report No. 350, Recommended Procedures for the Safety Performance Evaluation of High Features. The safety performance of the long-span barrier system was determined to be acceptable according to Test Level 3 (TL-3) of the NCHRP Report No. 350 criteria.