Mid-America Transportation Center


Date of this Version


Document Type



MwRSF Research Report No. TRP-03-104-00


Michigan Department of Transportation's Type B (W-beam) longitudinal barrier system was constructed and crash tested. The barrier design was constructed with a 2.66-mm (12-gauge) thick W-beam rail totaling 53.34 m in length. The W-beam rail was supported by twenty-five W152.13.4 steel posts, each measuring 1,830-mm long, and four standard BCT posts, each measuring 1,080-mm long. Each of the steel posts had a 152.203 by 360-mm long standard wood offset blockout. Post spacings were 1,905-mm on center.

The research study included full-scale vehicle crash testing, using a 3/4-ton pickup truck. The test vehicle impacted at a speed of 99.8 km/hr and an angle of 27.7 degrees. The test was unsuccessful due to the vehicle vaulting and landing on top of the guardrail with its right-side wheels contacting the ground behind the barrier system and then coming to rest on top of the downstream end of the guardrail. This unacceptable behavior was attributed to the failure of the W-beam guardrail to release properly from the guardrail posts. The safety performance of Michigan's Type B (W-beam) longitudinal barrier system was determined to be unacceptable according to Test Level 3 (TL-3) evaluation criteria specified in NCHRP Report No. 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. It was also concluded that the use of the routed wood blockouts did not contribute to the failure of the system.