Cost-Effective Treatment of Existing Guardrail Systems
Mitch Wiebelhaus, Karla Lechtenberg, Dean Sicking, Ronald Faller, Scott Rosenbaugh
A cost-effective means for upgrading existing guardrail systems with deviations from current practice (i.e., low-rail heights, antiquated end treatments, and improper installation) does not exist. As a result these systems remain on U.S. highways. Guardrail systems with deviations from current practice may not perform as intended, thus potentially resulting in fatalities and serious injuries from impacts with these safety devices. It is not plausible to eliminate fatalities and serious injuries from all guardrail system impacts. However, these risks could be reduced with the proper design, testing, installation, and maintenance of guardrail systems. This report offers recommendations for upgrading W-beam guardrail systems based on a benefit-to-cost analysis using the Roadside Safety Analysis Program (RSAP). This analysis was developed to simulate the most frequent and possible scenarios of existing W-beam guardrail systems with deviations from current practice. Before the analysis could be run, the field conditions and common deviations from current practice were reviewed and documented during a field investigation. This field investigation was conducted on rural arterial highways in the state of Kansas to determine the nature of existing guardrail systems with deviations from current practice. The most prominent barrier was the strong-post, W-beam guardrail. Deviations of the existing W-beam were low top-rail mounting-height, antiquated end treatments (i.e. turned-down and blunt-end terminals), rail damage, damaged and missing posts and blockouts, and insufficient length of need. The W-beam guardrail with low rail heights and turned-down and blunt-end terminals were the focus of the RSAP analysis. The varying guardrail system heights were modeled in RSAP by changing the level of containment of the W-beam guardrail system, and the antiquated end treatments were predefined features. The roadway and roadside features including obstacles (culverts and slopes) were modeled after those found in the field investigation. Finally, cost-effective safety treatments were recommended for existing W-beam guardrail system with low rail height and turned-down or blunt-end terminals which shielded culverts and slopes.
HIghway Safety, Benefit-to-Cost Analysis, Guardrail Height, Blunt End, Turned-Down, Culvert, Slope, RSAP, W-beam, Blockout