Estimation of Mobile Emissions Reduction from Using Electronic Tolls

The Baltimore Metropolitan Area is classified as a severe nonattainment area under the Clean Air Act Amendments of 1990. Consequently, it operates on a stringent emissions budget and is mandated to embark on mitigation measures. The area has been aggressively implementing emissions control and transportation demand management programs. One of the newest emissions control schemes in the Baltimore Metropolitan Area is the deployment of electronic toll collection (ETC) technology, locally known as M-Tag, at the three toll facilities (the Fort McHenry, Baltimore Harbor, and Key Bridge toll plazas). The ETC deployment, which began in the spring of 1999, has already enjoyed a significant market penetration. The objectives of the study described herein are twofold. First, use a microscopic simulation model to simulate the existing traffic situations at the Fort McHenry Tunnel toll facility, which is the largest toll plaza in the state of Maryland. Observed field data were used to validate simulation results. Second, capture the benefits inherent in the use of ETC technology by undertaking a comparative analysis of pre-ETC and post-ETC scenarios. The primary measures of effectiveness used are (1) increased throughput and hence reduced wait time at the toll plazas; and (2) reduced mobile emissions [hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NO_x)]. It was determined from the simulation and mobile emissions models that the current deployment level of M-Tag has improved the average travel speed by more than 125% and has decreased the mobile emissions rate by up to 41% at the Fort McHenry Tunnel toll plaza. It was concluded that the use of ETC is an effective tool for mitigating mobile emissions at toll plazas.