A bridge management system (BMS) is a systematic framework that formalises the decision-making process for bridge improvements. BMS decisions are analysed at two levels: (a) at the bridge level, BMS determines the optimal improvement alternative for a bridge; and (b) at the system level, BMS supports decision makers in developing systemwide strategies for optimal use of the limited bridge improvement budgets. A major BMS module is an optimisation algorithm for selecting the optimal combination of alternatives to maximise net benefits expected from the budget granted. The feasibility of implementing the Incremental Benefit-Cost (INCBEN) program for optimal allocation of the limited budgets to bridge improvement alternatives at the system level is investigated. Techniques and data exist for forecasting bridge agency costs and user costs, needed as input to INCBEN. Incremental benefits and costs are estimated from a base alternative. INCBEN ranks improvement alternatives in the decreasing order of their incremental benefit-cost ratios. These rankings are superior to those based on sufficiency ratings or level-of-service goals. INCBEN recommends near-optimal sets of bridge improvement alternatives under limited budgets. INCBEN selections under unlimited budgets are optimal and identical to the best alternatives selected by the economic analysis at the bridge level. INCBEN internally adds "do-nothing" alternatives to bridges without considering their consequences. This problem can be circumvented by manipulating the input data to ensure that the least-cost alternatives are funded first. (Author/publisher)
Samenvatting