Air pollution from vehicles is a factor included in the assessment of the environmental impact of highways. In order to carry out this assessment it is necessary to have a method of predicting pollutant levels for various highway configurations and traffic flows. A method of carrying out the prediction is described in this report; it uses data on traffic flows, vehicle speeds, road layouts and meteorological conditions and assumes gaussian type dispersion of the pollutants. The information on pollution is provided either in the form of levels at selected point locations or as pollution contours formed from a grid of a large number of points. The concentrations predicted by the first theoretical model were compared with measurements of carbon monoxide (taken as representative of present day vehicle pollution) at two sites and the predicted values were generally lower than those found at the sites. The prediction method was then modified after examining the various parameters used in the calculations and the modified method now predicts levels which are in acceptable agreement with the measured values. The prediction method can usefully be used in the comparative evaluation of the air pollution impact of alternative road schemes and also take into account the existing situations, although the absolute values predicted by the method are still to an extent approximations. (Author/publisher)
Abstract