The design, development, crash testing and evaluation of roadside safety appurtenances have traditionally been aimed at high-speed applications, i.e., 60 mi/h (96.6 km/h), and little attention has been given to lower-speed applications, e.g., 45 mi/h (72.5 km/h) or less. Currently, the same roadside safety appurtenances designed for high-speed applications are used for lower-speed applications since roadside safety appurtenances specifically designed for lower-speed applications are not available.
The objectives of this project was to crash test and evaluate the impact performance of a W-beam guardrail system with 12 ft-6 in (3.81-m) post spacing, intended for lower-speed applications, in accordance with criteria outlined in the new NCHRP Report 350. The proposed guardrail system will be tested at test level 2, i.e., at a nominal impact speed of 70 km/h (43.5 mi/h).
The 12 ft-6 in (3.81-m) post spacing guardrail system failed to meet the evaluation set forth in NCHRP Report 350. The test vehicle vaulted over the guardrail system with surprising ease. The unsatisfactory performance can be partially attributed to the lack of torsional rigidity of the W-beam rail element and the increased post spacing.