Heterogeneous traffic induced effects on vertical dispersion parameter in the near field of roadways - a wind tunnel study

The varying traffic parameters such as traffic volume, speed, shape and size, and terrain roughness conditions play a vital role on dispersion of pollutants in the near field of roadways. Simulation experiments were carried out in the Environmental Wind Tunnel (EWT) to evaluate the traffic induced effects on vertical dispersion parameter (sigma(z)) for heterogeneous traffic conditions in the near field of roadways for evaluating the effect of variations in traffic volume, terrain roughness condition and approaching wind direction. The model vehicle movement system was fabricated and made operational in the EWT, which allowed the variation in traffic volume, speed and wind road inclination. Sixty-six hydrocarbon tracer experiments were performed to evaluate sigma(z) in the near field of roadways for variable traffic volume, three terrain roughness conditions and two approaching wind directions (i.e., 90degrees and 60degrees). The values of sigma(z) for heterogeneous traffic conditions were found to be higher for low roughness conditions in comparison to other two higher roughness conditions for various traffic volumes and approaching wind directions.