Safety performance evaluation of the non-blocked Midwest Guardrail System (MGS).

The roadway width required to install a guardrail system with a 12-in. (305-mm) blockout is not always available. In response, proprietary non-blocked W-beam guardrail systems were developed and successfully crash tested. However, the use of proprietary systems requires the State Departments of Transportation to maintain inventory of specialized components. Therefore, a non-proprietary, non-blocked W-beam guardrail system was developed. The Midwest Guardrail System (MGS), with a 31-in. (787-mm) nominal top rail height, was chosen for modification due to its exceptional redirective capacity. For this research, the 12-in. (305-mm) blockout was removed, and a 12-in. (305- mm) long section of 12-gauge (2.66-mm) W-beam guardrail was utilized as a backup plate at rail-to-post connections. This design was successfully tested using a small car (test no. 3-10) and a pickup truck (test no. 3-11) according to the testing standards established in the Manual for Assessing Safety Hardware (MASH). As a result, the non-blocked MGS was recommended for use when roadway width was a limiting parameter. If width is not restricted, it is still recommended to use a 12-in. (305-mm) blockout as designated in the design drawings of the standard MGS.