The impacts of road traffic management on urban air quality

The effects of road traffic emissions on urban air quality are investigated, using long-term nitrogen dioxide (NO2) data. The effectiveness of the several traffic management measures that have been made in Dundee city centre, UK, within the last 5 years in relation to urban air quality is discussed. The information assessed during this study indicates that the annual mean NO2 levels at all the study sites are, at present, below the current EC and WHO (long-term) air quality standards for NO2 concentration in the ambient air. Traffic restrictions appear to be effective in protecting urban air quality. The annual mean NO2 concentration at two of the study sites is currently close to 40 mu g/m(3), a value published in the Air Quality Regulations 1997 for the air quality objective to be achieved by the year 2005. Proactive traffic management mitigation measures are proposed for these sites and a methodology for the consideration of traffic management alternatives, based upon traffic flow modal split, is described. Some measures proposed are based upon a survey of vehicle occupancy rates, carried out at the busiest of the four study sites. The methodology and assessment procedures presented should be invaluable to assessors of traffic management and local air quality management in a small city, both at the planning and at the auditing stage. (C) 1998 Elsevier Science B.V. All rights reserved.