Life-cycle benefit-cost analysis framework for ramp-metering deployments

The primary objectives of ramp metering are to reduce congestion on freeways by restricting the total flow entering the freeway and to discourage short-distance travelers from using the freeway. Life-cycle cost analysis of ramp-metering deployments has received attention in particular for identifying the strategy with the lowest cost. However, increasing concerns over the effects of congestion on the environment and increasing rates of accidents are urging decision makers to consider the environmental and social effects of ramp-metering deployments in addition to agency costs. This paper presents a high-level benefit-cost analysis framework for ramp-metering deployments. The framework was constructed in consideration of the triple bottom line of sustainability (i.e., economic, environmental, and social factors). More specifically, the framework is made up of four main components: (a) life-cycle cost analysis, (b) analysis of benefits achieved through travel time savings, (c) analysis of benefits achieved through reductions in energy consumption, and (d) analysis of benefits achieved through reductions in the number of accidents. A hypothetical case study is used to demonstrate the application of the framework. A sensitivity analysis is conducted to determine the effects of higher traffic demand on the benefits achieved. It is expected that the proposed framework can improve the high-level decision-making procedures of transportation agencies in regard to the deployment of ramp meters.