Introduction
As a major public transportation mode, urban rail transit has been widely used in china. Despite the
importance of the transportation sector for air pollution, little work has examined the air pollution effects
of transportation infrastructure directly. Researchers have disagreed about whether investment in urban
rail transit would improve air quality by taking cars off the road or harm it by encouraging more travel.
According to the forecast, transportation energy consumption and energy price will continuously increase
until 2030. To alleviate expensive energy consumption bill and environmental impact, developing a
model to evaluate reducing air pollution benefit model of urban rail transit is desirable, which is the
objective of this study. Some model have been developed and applied to evaluate reducing air pollution
benefit model of urban rail transit and other research applications.
A rich theoretical literature following Herbert Mohring has argued that rail transit is subject to
increasing returns to scale [1]. Ridership increases engender higher service frequencies, reduce the
average waiting times at stops, thus encouraging further ridership. The “Mohring Effect” implies that