BENEFIT COST STUDY FOR UNIQUE TRANSIT STRUCTURES

The San Francisco Bay Area Rapid Transit District (BART) is engaged in a comprehensive seismic retrofit of its 40 year old original system. Through design optimization and favorable construction bids, the Earthquake Safety Program has generated surpluses which have created the opportunity to increase the scope of the system upgrades. Options included seismic upgrades to the Berkeley Hills Tunnel (BHT) to accept various amounts of fault offset; and strengthening of selected aerial structures on the Fremont Line from a “life safety” to an “operability” level of seismic capability. BART conducted a feasibility and benefit-cost study for the BHT, along with a benefit-cost study for the already partially designed Fremont Line upgrades. The study included consideration of construction cost and schedule and impacts (ie, loss of service during retrofit construction), traffic delays and economic impacts both to BART riders and the greater Bay Area. Results of the study indicate that the largest impacts derive from the increased traffic congestion created due to the loss of BART for a period of time after an earthquake event. The direct mitigation costs and repair costs, and loss of fare box revenue, while important, are only part of the overall decision making process. The study effort represents an example of evaluating alternative projects using a benefit-cost analysis approach, and how an agency can use these analyses to provide input to decisions on where to allocate available funds.