Recently, vehicle emission has been regarded as the major
sources of air pollution in urban area and has attracted much
attention, especially at urban traffic intersection. At intersections,
vehicles frequently stop with idling engines during the red-light
period and speed up rapidly in the green-light period, which
generate higher velocity fluctuation and produce more pollutants
than any other situations such as cruise. Additionally, the interaction
of pedestrian movement and the influence of wind may
further cause the random dispersion of pollutants. It is very
difficult to simulate the effects of such dynamical factors on the