Part IV of the Environment Act 1995 (IRRD 874803) requires local authorities to undertake periodic reviews of air quality. The National Air Quality Strategy details the standards and objectives that relate to concentrations of certain pollutants, including nitrogen dioxide, PM10, benzene, 1,3-butadiene and carbon monoxide. If the predicted air quality is not expected to meet the objectives for the year 2005 then the local authority is required to designate an Air Quality Management Area and develop an action plan that should include a variety of traffic management measures to control the contribution from vehicles. Road traffic makes a large contribution to known emissions of key pollutants on a national, regional and urban scale. Although the emissions from individual vehicles will continue to fall as a result of stricter limits, increases in traffic are expected to cause the concentrations of some pollutants to exceed the objectives at some of the more heavily trafficked locations. The main pollutants of concern are nitrogen dioxide and PM10. This report reviews recent research on the impact of traffic management schemes on air quality. The review highlights the lack of hard evidence in terms of changes in air quality, with most of the studies relying on modelling rather than monitoring. However the evidence suggests that to achieve a general reduction in emissions from vehicles, traffic management schemes need to encourage a smooth driving behaviour. Individual traffic management schemes may locally have a beneficial impact on vehicle emissions, but any change in emissions per vehicle may be offset if traffic diverts to or from the managed area. Over the whole urban area, unless the measures are extensive the effects will generally be a lot less. The review also identified the lack of data on which to base estimates of the effectiveness of traffic management in reducing emissions. To overcome some of the deficiencies, research programmes based on two alternative budgets are proposed in the report. These it is felt will ultimately provide the scientific basis for future guidance on the impact of traffic management schemes on air quality and allow the effects to be estimated with much more accuracy. (A)
Samenvatting