A comparison of three highway line source dispersion models

This paper compares three idealized line source dispersion models that predict carbon monoxide concentrations near highways. The models are EPA HIWAY (Zimmerman, 1974), the original California Line Source (Beaton, 1972), and CALINE2 (Ward, 1975). The comparison includes a sensitivity analysis and model validation. A sensitivity analysis refers to an analysis of the dependence of normalized concentration to variations of several independent input parameters. Model validation is accomplished by comparing measured carbon monoxide concentrations with concentrations predicted by the models. The sensitivity analysis indicates that the EPA HIWAY model predicts higher pollutant concentrations than the two California models for oblique and crosswind cases. For parallel wind conditions, the California Line Source model predicts higher pollutant concentrations. A comparison of predicted and measured concentrations shows that all of the models overestimate concentrations for parallel wind conditions and underestimate concentrations for oblique and crosswind conditions.