TTI Research Supervisor:
Nauman M. Sheikh, P.E.
Associate Research Engineer
Texas A&M Transportation Institute
College Station, Texas 77843-3135
(979) 845-8955 [email protected]
Pooled Fund Technical Representative:
Michael Elle, P.E.
Design Standards Engineer
Minnesota Department of Transportation
395 John Ireland Boulevard, MS 696
St. Paul, MN 55155-1899
(651) 366-4622 [email protected]
The objective of the tests performed in this project was to evaluate the performance of a 31-inch tall W-beam guardrail system installed in a concrete mow-strip that reduces maintenance of the guardrail system by preventing growth of vegetation around the posts. Both wood post and steel post W-beam guardrail systems were evaluated. The tests were performed in accordance with the American Association of State Highway and Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH). MASH Tests 3-10 and 3-11 were performed for both wood and steel guardrail systems.
The 31-inch W-beam guardrail system with wood posts in concrete mow strip performed acceptably for MASH Test 3-10. However, during MASH Test 3-11, the W-beam rail element ruptured, allowing the 2270P vehicle to penetrate the installation. Consequently, the wood post W‑beam guardrail system in concrete mow strip did not perform acceptably for MASH TL-3 evaluation criteria for longitudinal barriers.
Subsequently, TTI researchers performed another MASH Test 3-11 on the wood post guardrail system with the posts at a reduced embedment depth of 36 inches. After loss of contact with the guardrail, the 2270P vehicle rolled and, therefore, did not perform acceptably for MASH TL-3.
The 31-inch W-beam guardrail system with steel posts in concrete mow strip performed acceptably for both MASH Tests 3-10 and 3-11. The steel post W-beam guardrail system in concrete mow strip is considered to have acceptable performance in accordance with the criteria for MASH TL-3 longitudinal barriers.