valid for 0°≤ θ ≤ 180°, the unit of the numerical coefficient 2.88642E-06 (km0.930771) results from the fitting methodology and it is such that dimensionless value of b is obtained for nv expressed in km−1 ( Mazzeo et al., 2012). Traffic induced turbulence (σv2 = bV2) is estimated using Eq. (5) and V taking into account traffic composition, but the different contributions generated by vehicles of different sizes are not explicitly identified. Mazzeo et al. (2012) used this expression and three other parameterisations of traffic-produced turbulence proposed by other authors into the scaling of air pollutants inside a street canyon to estimate hourly nitrogen oxides (NOx) concentrations at ground-level for leeward conditions and compared results with observations. The results obtained using b given by Eq. (5) were as good as obtained considering other parameterisations (which account for the differences in turbulence generated by vehicles of different size).