Failure of highway barrier systems and breakaway poles to perform as designed and tested under laboratory conditions has limited the effect of such systems in reducing the severity of highway collisions. In some instances, the placement of devices designed to reduce the severity of collisions has actually increased it.

This paper addresses the causes of system failure, and relates these causes to design detail, expected system performance, location criteria, installation specifications, and maintenance. The analysis of several real-world cases identifies the failure mechanism of the system, changes in current installation, and/or maintenance procedures that must be modified or discussed. The specific systems considered are roadside and median barriers and breakaway pole and sign supports. Each system will be discussed in terms of its intended application and performance.