Assessment of Safety and Traffic Operational Quality for Historic Stone Bridges

This paper presents the methodology developed for assessing the safety and traffic operational quality of 92 stone arch bridges within Hunterdon County, New Jersey. The methodology presented here was developed as part of a study conducted to provide recommendations on the maintenance and preservation of these bridges. As part of that study, four components were evaluated: traffic safety, traffic operational quality, structural stability, and historic significance. This paper focuses on the safety and traffic operational aspects of the study, and illustrates the methodology developed for quantifying them. To assess traffic safety, three different rating systems were used to quantify traffic safety operations, and rate the structures in their priority for improvements. The three traffic rating systems used were a comparison with current AASHTO design policy, the Bridge Safety Index developed at the Texas Transportation Institute, and the Widening Priority Rating developed by the writers. To assess traffic operational quality at these bridges, the Highway Capacity Manual methodology for two-lane highways was used, along with a queuing analysis method developed by the writers for narrow one-lane bridges. The traffic safety and traffic operational quality ratings were used in conjunction with historic significance information to produce a set of preservation recommendations for every structure.