Jensen, S.S., Ketzel, M., Nøjgaard, J. K. & Wåhlin, P. 2009: Air Quality Impact Assessment of Low Emission Zones in Denmark - Midterm Report. National Environmental Research Institute, Aarhus University. 64 pp. – NERI Technical Report No. 748.
The aim of this document is to report on the mid-term evaluation of the implementation of low emission zones in Denmark. The focus is on the quantification of the impacts on air pollution.
The Danish parliament decided on the low emission zone act on December 20, 2006. The act allows the largest five urban municipalities to implement low emission zones. The municipalies of Copenhagen and Frederiksberg implemented a low emission zone in September 1, 2008; the municipality of Aalborg on February 1, 2009, and the municipalities of Odense and Århus have decided to implement zones by July 1, 2001 and September 1, 2010, respectively.
The low emission zone act enables the municipalities to define the geographic extent of the zone. The act requires that diesel-powered trucks and buses are equipped with particle filters. From September 1, 2008 all trucks and buses with the Euro emission standard II or older have to meet the requirements and from July 1, 2010 also Euro emission standard III is included.
On behalf of the Danish Environmental Protection Agency, the Danish National Environment Research Institute (NERI) at Aarhus University carries out an evaluation of the impacts to air pollution of the low emission zones. Impact assessment is carried out of the full implementation of the low emission zone requirements.
This mid-term report includes results from on analysis of ”before” and “after” measurements of the air quality at a busy street canyon (Åboulevard) in Copenhagen. It also includes evaluation of NERI’s Operational Street Pollution Model (OSPM) by comparison of measurements and model predictions for Åboulevard to test the uncertainty of this model that used to model the impacts of the low emission zone requirements. An impact assessment is carried out for 138 busy streets in Copenhagen. Furthermore, a number of indicators for the effective implementation of the low emission zones have been evaluated. This comprises the number of issued low emission zone stickers to be visible in the front windshield of the vehicles, the number of dispensations, the number of subsidies for particle filters and the number of tickets for violating the zone regulations.
The ”before” measurement campaign was conducted during October 18 to December 17, 2004 and the “after” measurement campaign during November 11, 2008 to January 12, 2009. NOx, NO2, NO, CO, PM10, PM2.5 and particle size distribution were measured.
It was not possible to single out the effect of the low emission zone based on the analysis of the measurement campaigns. The potential impact is small compared to the uncertainties due to differences in the length of the campaigns and the long time between the campaigns. The observed decrease in concentrations is likely to be due to the continuous renewal of the car fleet. Observed minor reductions in the traffic level as well as a reduction in the fraction of heavy-duty vehicles contribute to the decrease, whereas an analysis of the meteorology (in terms of a dilution factor) showed that differences in meteorology had little impact on the observed decrease in concentrations.
The OSPM model was able to reproduce the observations at Åboulevard in 2004 and 2008/09 with an acceptable level of accuracy. Best results were obtained for NOx and NO2. PM10 and PM2.5 were also reproduced except for some special conditions for PM10 in 2008 and for PM2.5 in 2004. The diurnal variation and trends of CO observations were also well reproduced but the levels were underestimated. However, CO concentrations are well below air quality standards and CO is not included in the impact assessment.
The model is suitable for assessment of the impacts of the low emission zone requirements based on the model evaluation.
NERI’s OSPM model and the Urban Background Model (UBM) were applied for 138 streets in Copenhagen to estimate the impacts of the low emission zone requirements in 2010, 2015 and 2020. Separate results are reported for H.C. Andersens Boulevard - one of the busiest urban streets in Copenhagen with average daily traffic levels of 60,000 vehicles.
The predictions are based on a number of assumptions concerning growth in traffic, response of hauliers to the low emission zone requirements, the development in diesel share in the car fleet, the direct emission of NO2, and the effectiveness of particle filters.
An initial impact assessment of the low emission zone requirements can be made based on source apportionment derived from the traffic contribution to concentrations (street minus urban background concentrations) and receptor modelling. Estimation of the traffic contribution to PM10 concentrations at H.C. Andersens Boulevard in 2005-2007 shows that the average street concentration is 42.5 µg/m3, the urban background level 26.6 µg/m3 and the traffic contribution 15.9 µg/m3. The particle exhaust part constitutes 4.9 µg/m3 of the traffic contribution. Emission calculations for the street show that the heavy-duty vehicles account for 26% of particle exhausts. Particle filters can reduce emissions from these vehicles by 80% leading to a reduction in overall particle exhaust of 21%. The potential for reductions of PM10 concentrations in the street is 21%of 4,9 µg/m3, i.e. 1.0 µg/m3. Similar results are obtained for PM2.5.
The particle exhaust emission reduction for heavy-duty vehicles has been calculated to 78% for H.C. Andersens Boulevard based on the assumption that some heavy-duty vehicles will be equipped with particle filters and some will be replaced with newer vehicles that comply with the Euro V emission standard. PM10 and PM2.5 concentrations are reduced about 1.0 µg/m3 due to the low emission zone requirements.
The predicted reductions in the average street concentrations of PM10 and PM2.5 for the 138 streets in 2010 due to the low emission zone are modest. PM10 and PM2.5 concentrations in 2010 are predicted to decrease by merely 0.7 µg/m3 equivalent to about 2.5% for PM10 and about 3.5% for PM2.5.
Although the low emission zone requirements are not designed to reduce NOx emissions they are expected to have on impact of NOx emissions since some older heavy-duty vehicles are replaced with newer vehicles that comply with the Euro V emission standard.
For H.C. Andersens Boulevard the heavy-duty vehicles contribute by about 39% of NOx emissions in 2010. Heavy-duty vehicle NOx emissions will be reduced by 33% leading to a total reduction of 13%, taking vehicle categories into account.
A reduction of 3.4 µg/m3 is predicted for the average NO2 concentration for the 138 streets due to the low emission zone in 2010.
The air quality standard for annual average of NO2 is 40 µg/m3 in 2010. The number of exceedances without the low emission zone is predicted to be 65 out of 138 streets. This is significantly reduced to 35 exceedances in 2010 due to the low emission zone requirements.
Full report in pdf (2,71 MB)
