Light rail transit is considered as an environmentally sustainable transit option based on perceptions of its possible benefits on minimizing air pollution, energy consumption and greenhouse gas emissions. This study seeks to determine how light rail presence affects environmental sustainability in urban areas. For urban areas with existing light rail systems, this study also seeks to determine how light rail, urban area and public transit characteristics affect environmental sustainability. Environmental sustainability indicators were selected based on the environmental sustainability goals of minimizing air pollution, energy resource use and greenhouse gas emissions. Environmental sustainability goals were measured as air quality index, energy intensity, energy consumption per capita, carbon dioxide emissions intensity, and carbon dioxide emissions per capita as outcome variables. Using urban area and public transit data from 2000 to 2011, the impacts of light rail presence and other forms of rail transit on selected environmental sustainability indicators were estimated through a series of multiple regressions with light rail, urban area and public transit characteristics. Findings indicate that light rail presence affects environmental sustainability in varying degrees for each of the outcome variables. Light rail presence increases the predicted values for air quality index, but does not significantly affect energy intensity, energy per capita, CO2 intensity and CO2 per capita. Possible determinants of the selected environmental sustainability indicators include light rail ridership, light rail directional route miles, light rail operating expenses, and light rail passenger miles traveled. Housing density and employment density also significantly affect environmental sustainability indicators. Public transit ridership, directional route miles, and the number of vehicles operating at maximum service also affect environmental sustainability. The results of the study imply that light rail presence is not sufficient to influence environmental sustainability. Other factors are required, such as light rail transit ridership, which also influences how light rail transit affects the environmental sustainability in urban areas.
