Air quality impacts of speed-restriction zones for road traffic

This study investigates the air quality impacts of six 20 mph zones implemented in the North West of England. A monitoring study has been undertaken to measure the concentrations of nitrogen dioxide (NO2) and benzene in ambient air both before and after the implementation of the zones. An emissions estimation and simple dispersion modelling study has also been undertaken using traffic survey data collected at the zones at corresponding periods. The ambient air quality measurements and the modelling predictions did not show any significant impacts after implementation of the 20 mph zones.