Vehicle-to-infrastructure communications can be used for Electronic Open-Road tolling (EORT) systems, which offer several advantages such as smoother traffic flow, lower crash risk, and potentially reduced emissions and energy consumption. Agencies that can demonstrate emission reductions from proposed EORT systems are eligible for funding through Federal Highway Administration (FHWA)’s Congestion Mitigation and Air Quality Improvement (CMAQ) Program. The goal of this study was to estimate emission and energy reductions for EORT conversion projects to support development of a tool in the CMAQ Emissions Calculator Toolkit to assist agencies in quantifying benefits when applying for CMAQ funding. A three-tiered approach was applied, utilizing real-world traffic volume and speed data from two toll facilities on Interstate 90 near Boston, Massachusetts before and after EORT conversion, which took place in 2016.
Microscopic traffic simulation models were used to generate vehicle operating mode distributions for three tolling configurations: conventional full stop (queueing and idling through tolling area), conventional rolling cruise (low speed cruise, usually 10-20 MPH, through tolling area), and EORT free flow. These tolling configurations were applied to 27 scenarios on a four-lane, 2.5-mile traffic network consisting of three straight-line road segments: approach zone for deceleration and braking, tolling area, and departure zone for acceleration back to highway speed. The operating mode distributions were then used as inputs in the Motor Vehicle Emission Simulator (MOVES) and a multivariable linear regression was developed for each of the three tolling configurations and seven pollutants, including carbon monoxide, nitrogen oxides, Particulate Matter with diameters of 2.5 microns or less (PM2.5), PM with diameters of 10 microns or less (PM10), volatile organic compounds, and total energy consumption and greenhouse gases in carbon dioxide equivalent.
- The study found that for passenger vehicles (i.e., light duty vehicles) on a per mile basis, full stop conversions reduced PM2.5 up to 61 percent and energy consumption up to 28 percent, while rolling cruise conversions reduced PM2.5 up to 34 percent and energy consumption up to 10 percent.
- For heavy-duty vehicles on a per mile basis, full stop conversions reduced PM2.5 up to 62 percent and energy consumption up to 50 percent, while rolling cruise conversions reduced PM2.5 up to 31 percent and energy consumption up to 16 percent.