Assessing Air Quality Impacts of Managed Lanes

Impacts on transit bus performance and air quality were investigated for a case study high-occupancy / toll (HOT) lane project on a corridor of I-95 near Miami. Trends in air pollutant concentration monitoring data in the study area first were analyzed. Traffic movement prior to and after implementation of the HOT lanes was simulated using corridor micro-simulation (CORSIM). Emissions of carbon monoxide, nitrogen oxides, particulate matter, hydrocarbons, and benzene were estimated using MOBILE6.2. Finally, changes in ambient pollutant concentrations were estimated using AERMOD dispersion simulations. Results indicate decreased congestion on the corridor due to the HOT lane implementation, particularly for the northbound direction during the afternoon peak hours. Specifically, bus travel times were reduced by nine minutes, on average, during these hours. Emissions results were mixed, with small estimated increases for CO, NOx, PM10, and benzene and small decreases for HCs. Slightly higher ambient concentrations were found in most of the study area for the pollutants modeled (CO, NOx, and benzene), with the largest increases near the corridor. Overall, changes in both emissions and concentrations were small, indicating small impacts of the managed lane project on air quality. An additional outcome was the identification of factors contributing to uncertainty in the emissions estimation. Download the final report.

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