Air quality monitoring in the London Borough of Brent has indicated that concentrations of nitrogen dioxide (NO2) and particulate matter (PM10) would exceed the respective objectives of the UK Air Quality Strategy. Therefore, the London Borough of Brent (LBB) commissioned TRL Limited to undertake detailed air quality assessments in three areas where air quality exceedences had previously been identified. These were Wembley town centre, Harlesden town centre and the ‘Ikea’ junction on the North Circular Road at Neasden. These detailed assessments were based upon local traffic activity data which were obtained during 2005. Specific measurements undertaken within each study area included local traffic speed, traffic flows and vehicle type. Further refinements included the estimation of vehicle age, vehicle fuel type and engine size. Baseline oxides of nitrogen (NOX), particulate matter with an aerodynamic diameter of less than 10mm (PM10), carbon monoxide, volatile organic compounds, methane and carbon dioxide emissions were estimated for the study areas for a 2005 baseline and the future years of 2007 and 2010. For 2007 and 2010 estimates were derived for two scenarios: ‘business as usual’ and for the introduction of a low emissions zone (LEZ).
These detailed assessments showed that the establishment of an LEZ which included these three study areas would result in a reduction in PM10 emissions, and a slightly smaller reduction in NOX emissions, directly as a response to the introduction of cleaner vehicles into the vehicle fleet. The report concludes however that in 2007 and 2010, the LEZ option, in each of the study areas would have a marginal impact on reducing NO2 and or PM10 concentrations. The report considers both the emissions and air pollution modelling uncertainties and recommends how these might be addressed through refinements in those input data.

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