As a part of a study designed to relate accident experience on the interstate system to its various geometric design characteristics, the effect of guardrails on accident severity at bridge structures and sign posts and the effect of lateral clearances at bridge structures on accident occurrence and severity were studied. Data used in these analyses were collected by 16 state highway departments and represent approximately 2,000 miles of highway. Mileage was computed for both directions of travel. The results of a statistical analysis of property damage costs indicate that the presence of guardrails at overpasses , bridges, underpasses, and sign posts reduce the property damage costs of single-vehicle accidents and that increased minimum lateral clearances at overpasses and bridges reduce accident rates and property damage costs. (Author/publisher)
Abstract