NCHRP Report 350 Compliance Test 3-11 of the Modified G4(1S) Guardrail with Timber Blockouts (FHWA-RD-96-175)

The W-beam, strong-steel-post, G4(1S) guardrail system is one of the most commonly used guardrail systems on the nation's highways. This guardrail system successfully met all evaluation criteria set forth in National Cooperative Highway Research Program (NCHRP) Report 230. However, with the adoption of NCHRP Report 350 by the Federal Highway Administration (FHWA) as the official guidelines, it became necessary to evaluate the G4(1S) guardrail according to the new guidelines. One key change in NCHRP Report 350 is the replacement of the 2044-kg passenger car with the 2000-kg pickup truck (2000P) as the standard test vehicle. There was concern that the G4(1S) guardrail system may not perform satisfactorily to contain and redirect the 2000P vehicle.|Under a previous FHWA study, the G4(1S) system was crash tested in accordance with NCHRP Report 350 test designation 3-11, i.e., impact by the 2000P test vehicle at a nominal speed and angle of 100 km/h and 25 degrees. The guardrail successfully contained and redirected the test vehicle, but the vehicle rolled over on its side after exiting from the test installation and the performance of the guardrail system was judged to be unsatisfactory.|The report presents the results of a crash test on a modified G4(1S) W-beam guardrail system with timber blockouts. The crash test conducted was a repeat of NCHRP Report 350 test designation 3-11. The modified G4(1S) W-beam guardrail system with timber blockouts successfully contained and redirected the test vehicle, which remained stable during and after the impact sequence, and was judged to have performed satisfactorily in accordance with evaluation criteria set forth in NCHRP Report 350 for a test level 3 (TL-3) guardrail system.