COMPARING AIR POLLUTION FROM FERRY AND LANDSIDE COMMUTING

Marine engines from passenger ferries are known to be a significant and growing air pollution source category in some locations, but sparse data and analytical difficulties have prevented rigorous comparisons of marine and on-land passenger travel. This study uses data gathered in the San Francisco Bay Area to model emissions from three passenger ferries and the matching on-land travel that would be used by commuters if ferry service were not available. The results are analyzed parametrically for levels of ridership and induced travel demand, and for new technologies, including selective catalytic reduction and natural gas fuel. Results indicate that under some conditions, passenger ferries reduce some emissions, including particulate matter emissions, relative to the matching on-land service but increase others. Emissions of nitrogen oxides (NOx) are particularly problematic, with ferry commuting always leading to increased NOx emissions, even with the most advanced technologies. Some of the other emissions comparisons are sensitive to modal split, ridership or induced travel demand. Emissions from existing ferry operations can be reduced significantly with new technologies. However, without technologies that can reduce emissions, the air pollution impacts of ferry commuters will be much higher than those from onland commutes. These results suggest that ferry scenarios that conform to regional mobility and air quality planning goals should be integrated into broader transportation planning considerations.