Development of Emission Factors for an Urban Road Network Based on Speed Distributions

AbstractTo investigate the feasibility of incorporating speed distributions instead of average speeds to develop emission factors for emission estimations, this research collects large amounts of emission and traffic activity data. First, the relationship between emission factors and average speeds is developed. Second, speed distributions during daytime hours for classified roads are analyzed to find the speed distribution on the expressway followed the bimodal distribution; speed distributions on arterials and collectors followed the same distribution pattern, but with a single peak. Third, the research develops emission factors for the road network based on speed distributions, then compared these with those found using the traditional average-speed-based method. A comparative analysis shows even though both emission factors for these two distinct methods presented a similar variation trend, the results from the average-speed-based method were lower. The research identifies two reasons for those differ...