The purpose of this dissertation is to develop a methodology to estimate the temporal Environmental Traffic Capacity (ETC) for urban streets. The approach constitutes the main procedure of ETC calculation and an experimental process of developing an emission inventory. The major contribution of this study includes results that support the development of traffic control policies to alleviate the negative impacts of on-road emission sources, and suggestions for future research to optimize road capacity with respect to air quality.

A framework is proposed for the combination of the traffic volume model developed in this dissertation with the Danish OSPM (Operational Street Pollution Model), a dispersion model, to calculate the ETC. The time-dependent traffic volume is connected with the time-dependent ETC via the average speed generated by a traffic speed-flow model. The basis for estimating the ETC is an inverse modeling of the OSPM. This method is improved by a further inverse modeling of the traffic volume model, which was developed in this research, to obtain the values of ETC for each hour under consideration.

An experimental process is designed for the development of a weight-based emission inventory. A probability approach is applied to calculate the emission factors based on speed and acceleration variations. This method results in a weighted-emission inventory by a series of speed-acceleration combinations, for each of three categories of test vehicles, of CO₂, CO, HC, and NO_x emissions. Using a real-site case study, the implementation of the methodology to estimate the ETC of a road section in a congested area for ten consecutive hours on a regular weekday is demonstrated.

It has shown that the ETC is closely related to the joint effects of meteorology and traffic conditions. Two options of improvements using the ETC to relieve the traffic pollution are also presented at the end of the case study. The result indicates that increasing the speed limit of the whole area has better effect on reducing the traffic pollution than reconfiguring the physical dimension of the road section.