Speed estimation for air quality analysis

Average speed is an essential input to the air quality analysis MOBILE6 model for the calculation of emissions factors. Traditionally, speed is obtained from travel demand models; however, such models are not usually calibrated to speeds. Furthermore, for rural areas where such models are not available, no reliable method is available for estimating speed. In this study, we developed a procedure based on the model in the Highway Economic Requirement System to estimate average speed using as input various data such as roadway characteristics and traffic conditions. The model was confirmed to be powerful based on the statistical comparisons between the estimated and measured speeds. Various implementation issues including the impact of data quality and potential applications are also discussed.