Impact of low emission zones and local traffic policies on ambient air pollution concentrations

BackgroundEvaluations of the effectiveness of air pollution policy interventions are scarce. This study investigated air pollution at street level before and after implementation of local traffic policies including low emission zones (LEZ) directed at heavy duty vehicles (trucks) in five Dutch cities.MethodsMeasurements of PM10, PM2.5, ‘soot’, NO2, NOx, and elemental composition of PM10 and PM2.5 were conducted simultaneously at eight streets, six urban background locations and four suburban background locations before (2008) and two years after implementation of the policies (2010). The four suburban locations were selected as control locations to account for generic air pollution trends and weather differences.ResultsAll pollutant concentrations were lower in 2010 than in 2008. For traffic-related pollutants including ‘soot’ and NOx and elemental composition (Cr, Cu, Fe) the decrease did not differ significantly between the intervention locations and the suburban control locations. Only for PM2.5 reductions were considerably larger at urban streets (30%) and urban background locations (27%) than at the matching suburban control locations (20%). In one urban street where traffic intensity was reduced with 50%, ‘soot’, NOx and NO2 concentrations were reduced substantially more (41, 36 and 25%) than at the corresponding suburban control location (22, 14 and 7%).ConclusionWith the exception of one urban street where traffic flows were drastically reduced, the local traffic policies including LEZ were too modest to produce significant decreases in traffic-related air pollution concentrations.

► We evaluated LEZ directed at old trucks using measurements of different pollutants.
► We did not find a measurable effect of the LEZ on traffic-related air pollutants.
► Multiple local traffic policies reduces traffic-related air pollution in one street.