If 180°< θ < 360° and U > 2 m s−1, the receptor receives the re-circulating part of the pollutants in the street and in these cases the contribution of traffic-induced turbulence to the dilution of pollutants can be neglected, so b = 0. However, for meteorological conditions with 180°< θ < 360° and low wind speeds (U ≤ 2 m s−1) b is evaluated using Eq. (5).
Eqs. (1), (2), (3), (4) and (5) constitute SEUS model for inert pollutants. In summary, the application of SEUS model to estimate inert pollutant concentrations requires the following input information: street canyon dimensions, traffic flow and composition in the street, air pollutant emissions, ambient wind speed and direction, and background concentration contribution from sources outside the street.