The California Department of Transportation (Caltrans) owns and operates nine toll bridges throughout the state. The current toll collection system, known as a Toll Registration, Audit and Collection (TRAC) system, had been scheduled to be replaced by an ETC system. The Carquinez Bridge ETC project is a pilot project for the statewide toll-bridge improvement project.
The intended benefits of the Electronic Toll Collection (ETC) system are to reduce overall toll-collection costs, provide an acceptable level of service for toll patrons, increase data quality, and reduce traffic congestion, air pollution, and fuel consumption on toll bridges.
This analysis was used to evaluate the net benefits of the pilot ETC project and by extension, the statewide toll-bridge improvement project.
Caltrans is concerned with providing safe, economically efficient service on its toll bridges.
The base case used in this analysis was the existing manual TRAC system.
The only alternative considered in this case was the ETC system, in which all toll lanes are equipped with automatic toll collection devices.
For this analysis the benefit-cost and net benefits methods were used.
Changes in the tolling system on the Carquinez bridge immediately affect motorists using the bridge. The communities around the bridge are also affected by changes in congestion and the accompanying changes in air and noise pollution. Because the bridge is state owned, the state budget is affected by any changes in toll revenue and bridge operating costs.
This analysis considered a time period of 10 years.
The benefits considered in this analysis were monetary savings to the toll agency and patrons, time savings to patrons, emission reduction, and safety improvements. The following estimate parameters were used to calculate these benefits:
The following table provides the total distribution of calculated benefits:
The costs to the toll agency were calculated at $3,037,421. The increase in cost to toll patrons was calculated at $239,449. This led to a combined cost for the project of $3,276,870.
A sensitivity analysis was performed to investigate the effects of changing assumptions on the net benefits and distribution of benefits and costs. The following table summarizes the results:
Models were used to estimate costs, travel time, and environmental impacts. The average annual traffic growth rate of 3 percent was derived from traffic data for the bridge over the last 20 years.
The analysis does a good job of analyzing how the project affects each of the major stakeholders. It uses sensitivity analysis effectively to assess the effects of uncertainties. However, most of the benefits are derived from travel time savings. These savings were based on assumptions regarding acceleration and deceleration and toll-taking service times from a Caltrans feasibility study. Given their importance in the final result, it would have been better to use actual measurements of time saving made at the bridge itself.
Li, J., D. Gillen, and J. Dahlgren. "Benefit-Cost Evaluation of the Electronic Toll Collection System: A Comprehensive Framework and Application". Transportation Research Record 1659, TRB, National Research Council, Washington, D.C., 1999, pp. 31-38.
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