Assessing the impact of transport interventions on air quality

Local transport authorities have recently produced their second local transport plans. Government guidance covered technical and financial issues and set out a number of objectives and targets. Requirements included setting a target related to air quality and providing evidence of tackling climate change. AEA Technology were asked by Surrey County Council to advise on these issues and effective partnership working produced a new approach to assessing the impact of transport interventions on air quality. The core of the method is a relatively simple model, but the key to success is the development of links between measures (such as travel plans or bus quality partnerships) and the model parameters. The outcome is a process whereby the impact of such measures on the concentration of pollutants can be calculated. For example, traffic reduction measures (including travel plans) have been shown to be effective in reducing the concentration of nitrogen dioxide at critical locations in Spelthorne. A similar approach is used to calculate impacts on CO₂ emissions and hence to assess the contribution to climate change.