Improving air quality is emerging as an important factor in transportation planning. Recent directives in the UK reflect experience in other countries, especially the USA, where air quality analysis is a standard part of transportation impact assesment. Policy initiatives to reduce vehicle emissions include promoting transit use, transit oriented development, carpooling, bicycles and walking as alternatives to single occupancy vehicle trips. This paper examines the potential of mode shift from automobile to transit to mitigate rising vechicle emissions, using Orange County, California as a case study. The evaluation utilises the results of a research project sponsored by Orange County Transportation Authority and the South Coast Air Quality Management District to develop a Transit System Analysis Model (TSAM) that could analyse the impact of changes in transit demand. Orange County is located south of Los Angeles and is undergoing rapid population and employment growth. The analysis integrates trip data from a travel demand model with an air quality model to predict the impact of planning and policy changes. TSAM uses a Geographic Information System (GIS) to integrate and map the different data sets including land use, demographic and transportation data. The paper describes how TSAM operates, how the workflow of integrating and calibrating the trip data and emission factors model is accomplished, and how the results are compiled geographically for mapping and further spatial analysis. Specifically, a case study of a proposed bus route restructuring exercise will be evaluated.
Abstract