Development of User Cost Model for Movable Bridge Openings in Florida

The Florida Department of Transportation (FDOT) is currently implementing the AASHTO Pontis® Bridge Management System (BMS) to support network-level and project-level decision making at the state and district levels. User cost models in the Pontis BMS quantify in economic terms, the potential safety and mobility benefits of maintenance, repair and replacement of bridge structures. Movable bridge openings force vehicles traveling over the bridges to be held in queues and this results in extra travel time for motorists. The extra travel times are quantifiable as traffic delays costs, which are indirectly borne by commerce and the motoring public, and can be used in an economic analysis to justify the replacement of movable bridges. This thesis presents a study that involved the collection of Florida specific data on vehicular and vessel traffic, including vehicle queue counts, average daily traffic, hourly distribution of vehicular traffic, movable bridge openings, vessel counts and vessel heights at six (6) selected, geographically unbiased, movable bridge sites within the Florida. The data were analyzed and used in development of a user cost model for movable bridge openings for implementation in the Florida Pontis BMS. The movable bridge openings were modeled as bottleneck incidents on the roadways carried by the movable bridges and a deterministic queue model was used in analyzing the resulting delays to vehicular traffic. The developed model was used in a network analysis of Florida's inventory of 147 movable bridges to estimate the economic benefits of bridge replacement projects with the objective of correcting load carrying capacity deficiencies and elimination of traffic delays that were caused by the movable bridge openings. Results obtained showed that the savings in delays to vehicular traffic caused by movable bridge openings would contribute about eight (8) times more than the economic benefits that may be obtained from strengthening movable bridges in Florida.