Evaluation of Truck Impact Hazards for Interstate Overpasses

Increased freight activities on Interstate highways escalate the risk of collision between trucks and overpass bridges. Although such events are rare, the consequences of such a collision may be catastrophic. Many overpass bridges were designed and constructed in the early years of development of the Interstate highway system and therefore did not meet the requirements specified in AASHTO's Load and Resistance Factor Design Bridge Design Specifications. In this study, 5-year truck run-off-the-road crash data, information on Interstate highway geometric characteristics, and traffic information were collected to develop crash prediction models for bridge bents. The bent-based predictive methods improved the collision risk estimate by evaluating the individual bents of a bridge on the basis of roadway geometrics and traffic conditions. The detour costs subsequently measured on the basis of the additional road user costs caused by the failure of a bridge were used to assess the importance of a bridge quantitatively. As a result of this study, a bridge index was developed from both the collision risk and detour costs. This study could provide guidance to departments of transportation to develop mitigation plans for bridges with high collision risk indexes.