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EFFECTS OF TRAFFIC SPEED ON THE AMBIENT POLLUTANT CONCENTRATION NEAR ROADWAYS
Citation:
Petersen, W.B., R. Eskridge, S.T. Rao, AND V. Pagnotti. EFFECTS OF TRAFFIC SPEED ON THE AMBIENT POLLUTANT CONCENTRATION NEAR ROADWAYS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/D-84/102.
Description:
In the numerical roadway model, the vehicle wake diffusion is dependent upon the turbulent kinetic energy, which is proportional to the square of the relative wind speed on the moving vehicles. This model predicts that turbulent mixing and hence pollutant concentration on and downwind of the roadway are dependent on the vehicle speeds. The Long Island Expressway CO data provide an opportunity to test the theoretical predictions on the effect of traffic speed on the ambient concentrations. It is observed that the traffic speed does not affect the dispersion process as long as the ambient atmospheric conditions are neutral or unstable. Sufficient data are not available to quantify the role of traffic speed on the ambient concentrations downwind of the roadway under stable atmospheric conditions. Since commonly used Gaussian dispersion models do not account for traffic generated turbulence properly, it is possible that the current versions of these models underestimate pollutant concentration adjacent to the roadway under stable atmospheric conditions with low traffic speeds.