TTI Research Supervisor:
Chiara Silvestri Dobrovolny, Ph.D.
Associate Research Scientist
Texas A&M Transportation Institute
College Station, Texas 77843-3135
(979) 845-8971 [email protected]
Pooled Fund Technical Representative:
Ali Hangul, P.E.
Civil Engineering Manager I, Design Division
Tennessee Department of Transportation
James K. Polk State Office Building
Nashville, TN 37243-0348
(615) 741-0840 [email protected]
The purpose of the test reported herein was to assess the performance of the 28-inch W-beam guardrail system with 8-inch composite blockouts raised on steel posts according to the safety-performance evaluation guidelines included in the American Association of State Highway and Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH). The crash test was performed in accordance with MASH Test 3-11, which involves a 2270P vehicle impacting the 28-inch W-beam guardrail system with raised composite blockouts at a target impact speed and impact angle of 62 mi/h and 25 degrees, respectively. The outcome of this study can be used to complement any existing guideline regarding the procedure of raising blockout mounting height on steel posts to achieve recommended rail height for a W-beam guardrail.
The 28-inch W-beam guardrail system with raised composite blockouts contained and redirected the 2270P vehicle. The vehicle did not penetrate, underride, or override the installation. Maximum dynamic deflection during the test was 52.6 inches. Detached blockouts did not penetrate or show potential for penetrating the occupant compartment, or present undue hazard to others in the area. No reduction or intrusion of the occupant compartment occurred. The 2270P vehicle remained upright during and after the collision period. Maximum roll and pitch angles were 32 degrees and 12 degrees, respectively. Occupant risk factors were within the preferred limits specified in MASH.
The 28-inch W-beam guardrail system with composite blockouts raised 4 inches performed acceptably for MASH Test 3-11. For the test conducted in this study, a guardrail height of 28 inches was chosen, and rail splices were positioned on posts. These selections represent the worst case condition for testing.
Taller rail heights, offset rail splices, and raising of the blockout less than 4 inches are considered acceptable based on the results of this more critical test. The practice can be used to raise the height of a deficient guardrail to an acceptable height (i.e., 28 inches or greater), or could be used to raise the height of existing guardrail to improve performance (e.g., 31-inch rail height).
W-Beam Guardrail with Raised Blockouts prior to Test