An improved line source model for air pollutant dispersion from roadway traffic

Gaussian plume models, which are widely used to model atmospheric dispersion, provide an exact analytical solution for line sources such as roads only when the wind direction is perpendicular to the road. Some approximations have been developed to provide an analytical formula for a line source when the wind direction is not perpendicular to the road; however, such formulas lead to some error and the solution diverges when the wind direction is parallel to the road. A novel approach that reduces the error in the line source formula when the wind direction is not perpendicular to the road is presented here. Furthermore, a combination of analytical and numerical line source solutions is used to better represent cases where the wind direction becomes parallel to the road. The improved model was implemented in the Polyphemus modeling platform and it was successfully evaluated against a reference solution as well as observations obtained near a roadway in eastern France.