Jensen, S.S., Ketzel, M., Nøjgaard, J. K. & Becker, T. 2011: Hvad er effekten af miljøzoner for luftkvaliteten? - Vurdering for København, Frederiksberg, Aarhus, Odense, og Aalborg. Slutrapport. Danmarks Miljøundersøgelser, Aarhus Universitet 110 s. –Faglig rapport nr. 830. http://www.dmu.dk/Pub/FR830.pdf
The purpose of establishing the low emission zones is to improve the health of citizens in the largest cities in Denmark by reducing air pollution from particulates. The low emission zone Act requires trucks and buses in a low emission zone to be equipped with particle filters. The requirements apply to trucks and buses that per September 1, 2008 only meet the Euro 2 emission standard (or older standards) and the requirements were tightened further per July 1, 2010 to include the Euro 3 emission standard. The Municipality of Copenhagen and the Municipality of Frederiksberg introduced a common low emission zone from September 1, 2008, Municipality of Aalborg from February 1, 2009, Municipality of Odense from July 1, 2010 and Municipality of Aarhus from September 1, 2010. The National Environmental Research Institute (NERI), Aarhus University has been responsible for conduction an evaluation of the effects on air quality of the low emission zones financed by the Danish Environmental Protection Agency. A Mid-term report has been published in 2010 (Jensen et al. 2010), which focused on assessing the effect on air quality of the low emission zones in Copenhagen and Frederiksberg, that were the first municipalities to implement the low emission zone requirements. In the present final report, the effects on air quality are re-evaluated for Copenhagen in light of updated vehicle fleet and traffic information and emission assumptions, and new assessments are carried out for Aarhus, Odense and Aalborg.
Effect Assessment based on measurements from H.C. Andersens Boulevard
An analysis of measurements of air quality at H.C. Andersens Boulevard in Copenhagen before and after introduction of the low emission zone has been carried out. The analysis is based on extensive measurements from the Particle Project with the aim to isolate the effect of the low emission zone. H.C. Andersens Boulevard is one of the busiest streets in Copenhagen and the Particle Project has carried out measurements of different parameters for particulate matter at H.C. Andersens Boulevard and at an urban background location and a regional background. The idea of the study is to compare an observed reduction in the difference between street and urban background concentrations (street contribution) with a modelled emission change calculated with the emission module of the OSPM model without including the impact of the low emission zone. If the observed concentration change of the street contribution is greater than the modelled emission change then this difference is an indication of an effect of the low emission zone on air quality.
The effects of the low emission zone on composition of the car fleet based on license plate information coupled to the Motor Registry
For the evaluation of effects of the low emission zones in the Mid-term report, assumptions were established on how the fleet of heavy-duty vehicles most likely would respond to the low emission zone requirements. How many heavy-duty vehicles would be equipped with particle filters? and how many would be replaced with newer emission standards due to the low emission zone? These assumptions are crucial for estimation of the effects for emissions and air quality. One of the ways in which these assumptions can be tested is through registration of license plates coupled to the Motor Registry. Video recording of license plates at the street of Åboulevard in Copenhagen was carried out for long periods in 2008 and 2010, and these license plate data is coupled to the Motor Registry. The Motor Registry includes data which makes it possible to determine the emission category (Euro emission standard) of each vehicle. The main purpose of recording of license plates was to evaluate the assumptions that NERI has to set up in order to calculate the effect of low emission zones for air quality.
Comparison of modelled and observed concentrations
Comparison of modelled and observed concentrations for 2010 for four urban background monitor stations and five street monitor stations under the Danish Air Quality Monitoring Program (NOVANA) was carried out in order to illustrate the uncertainty in the subsequent model calculations on selected streets in the low emission zones.
Sensitivity analysis of impacts of different input assumptions on predicted concentrations
An analysis of model results under different input assumptions for H.C. Andersens Boulevard in 2015 has been conducted to illustrate the sensitivity of different input assumptions on predicted concentrations.
Modelled concentrations at selected streets in the low emission zones
Model calculations have been performed for 138 busy streets in Copenhagen and Frederiksberg, 55 streets in Aarhus, 40 streets in Odense, and 31 streets in Aalborg. Calculations are carried out without and with the low emission zone requirements in 2010, 2015 and 2020.
Applied air quality model system
Air quality calculations have been carried out with an inter-linked model system consisting of a regional long-range transport model (DEHM), an urban background model (UBM) and a street air quality model (OSPM) and associated meteorological and emission data. The AirGIS system has been used to automatically generate street geometry and traffic input to the OSPM model based on digital maps for roads and buildings, enabling efficient calculations for many locations.
Modelled meteorological data from the meteorological model MM5 is applied, and emission data for the DEHM model is based on a number of European and global emission inventories.
Emissions for the UBM model are based on a new emission database (SPREAD) developed by NERI which makes a geographical distribution of national emissions on a 1km x 1km grid. The database includes emissions from all sources (traffic, industry, energy, etc.) whereas previous assessments were based solely on traffic sources.
Traffic emissions at street level are calculated by the emission module of the OSPM model which is based on the EU COPERT 4 emission model. The emission model requires information about the car fleet and its distribution by vehicle category, fuel type and emission standards. The latest updated version of the COPERT 4 model is implemented, and provides a further breakdown of the emission categories into weight sizes for buses and trucks compared to former versions.
The municipalities of the low emission zones have provided updated traffic data for Copenhagen and Frederiksberg and new traffic data for Aarhus, Odense and Aalborg. Traffic data includes Average Daily Traffic (ADT), vehicle composition (passenger cars, vans, trucks and buses), and travel speeds.
Assessments based on measurements on H.C. Andersens Boulevard
In the analysis of measurements, the reduction in EC (elemental carbon), benzo(a)pyrene (PAHs), PM2.5, N (number of particles), NOx, CO, benzene and toluene was calculated by linear regression analysis over a three-year period from 2008 to 2010. To isolate the effect of the low emission zone based on analysis of measurements is technically a difficult task. Small concentration changes have to be assessed over a relatively short time period of three years that is affected by factors like meteorology, uncertainty of measurements and data analysis, and an overall reduction in emissions resulting from the continuous renewal of the car fleet. Under these reservations, the introduction of the low emission zone is assessed to have reduced the PM2.5 street contribution at H.C. Andersens Boulevard by about 0.7 µg/m3 during the period January 2, 2008 to December 15, 2010. For comparison, the street concentration is about 14.3 µg/m3 and the street contribution is about 5.8 µg/m3 in the beginning of 2008. PM2.5 is measured with the TEOM method and the street concentrations are therefore about 30% lower than the true concentrations. The observed reduction in PM2.5 is further supported by the fact that related parameters like EC, PAH and particle number also are reduced.
The impacts of the low emission zone on the car fleet based on license plate information coupled to the Motor Registry
In assessing the impacts of low emission zones, it is of particular interest to know how the low emission zone affects the emission classes of the car fleet and the number of heavy-duty vehicles with retrofitted particle filters. Although the Motor Registry in principle should include this information, it turns out that the information is not consistently recorded. For example, the emission class is only registered in 2% of all cases, 5% for passenger cars and vans, 65% for buses and 97% for trucks. Therefore, it has been necessary to group the registered vehicles into emission classes based on information about the registration date of the vehicle and start and end dates of the different emission standards.
Analysis of the subset of vehicles that were registered by emission class in the Motor Registry shows that in most cases there was a match between the registration date of the vehicle and the assumed Euro class, but it was also clear that there are some registrations where the registration date was before the entry date of the Euro class. This indicates that a new emission standard is sold before it becomes mandatory. It is not possible from the available data to include this effect in the description of the car fleet.
In the Mid-term report, the impacts of the low emission zone were established based on assumptions of how the vehicle fleet for the heavy-duty vehicles was likely to respond to the requirements of the low emission zone. Based on the new license plate information it is now possible to test these assumptions. For buses it was assumed that all Euro 3 buses and 50% of the Euro 2 buses would be retrofitted with particle filters and other buses would be replaced by newer buses with the Euro 5 or later.) For trucks it was assumed that all Euro 3 trucks would be retrofitted wit particle filters and older trucks would be replaced by newer vehicles (Euro 5 or later). The analysis of the license plate information broadly confirmed these assumptions.
Based on the new information from the recorded license plates and information from the Motor Registry new assumptions for the vehicle fleet with and without the low emission zone was established for 2010, 2015 and 2020. These new assumptions are used in the revised calculations of the effect of the low emission zone on air quality.
Comparison of modelled and observed concentrations
A comparison of modelled annual concentrations of PM2.5, PM10 and NO2 and measurements was carried out at street and urban background monitor stations in 2010 for the cities with the low emission zones to illustrate the uncertainty of the applied model system and input data.
The comparison shows that there is a good agreement between calculated and measured levels of PM2.5 and PM10 in the regional background (after up-scaling of underestimated regional levels), and modelled urban background concentrations are within -4% to 10% of observed concentrations disregarding Aalborg where measured urban background concentrations are likely to be affected by temporary construction at the harbour front. Street concentrations of PM2.5 and PM10 are within -7% and 11%, again disregarding Aalborg.
The comparison for NO2 shows that calculated urban background concentrations are within -21% to 19% of the measurements at urban background stations with an average close to zero. Calculations of street concentrations differ between -16% and 12% with a more systematic underestimation by the model system, since four out of five streets have underestimation of NO2. Therefore, it is more likely that the model system will underestimate NO2 concentrations than overestimate. There is a systematic underestimation of NOx which suggest that traffic emissions are underestimated.
Sensitivity analysis of the impacts of different input assumptions on predicted concentrations
An analysis of model results under different input assumptions for H.C. Andersens Boulevard in 2015 has been conducted to illustrate the sensitivity of different input assumptions on predicted concentrations. The analysis is based on calculations carried out within the last few years in different projects. The calculations show a range of NO2 concentrations from about 40 ?g/m3 to 46 ?g/m3 depending on the assumptions. The latest assessment of annual NO2 concentration in 2015 for H.C. Andersens Boulevard is 40.45 ?g/m3 which is just below the threshold value which must exceed 40.5 ?g/m3 to be recorded as an exceedance. This assessment includes the latest assumptions for the vehicle fleet, emission factors and traffic and is the most likely based of the existing knowledge.
Modelled concentrations at selected streets in the low emission zones
Effects of the low emission zone on particle emissions were assessed for H.C. Andersens Boulevard in 2010, 2015 and 2020. Tail-pipe emissions from heavy-duty vehicles were reduced by 60% in 2010 due to a combination of the low emission zone in 2010 and environmental requirements to public bus service. This is a result of some Euro 3 and older vehicles being retrofitted with particle filters and some being replaced with newer Euro 5 vehicles which have lower emission standards. The reduction in exhaust emissions are 16% compared to total emissions from all vehicle categories. The total reduction in emission of PM10 (exhaust and non-exhaust) and PM2.5 (exhaust and non-exhaust) are 4% and 8%, respectively. The reduction is less for PM10 compared to PM2.5 since exhaust emissions for PM10 constitutes a smaller proportion of the total emission (exhaust and non-exhaust). Non-exhaust includes road, tire and brake wear and re-suspension of particles. The reductions are smaller than predicted in the Mid-term report due to different assumptions about the vehicle fleet, emission factors and traffic data.
The average effect on air quality of PM2.5 and PM10 are about 0.2 ?g/m3 for all streets in all the cities with low emission zones in 2010, and the maximum effect is up to 0.7 ?g/m3. The average reduction in street concentrations of PM2.5 is equivalent to 1.5% and 1% for PM10. The reason why the reduction is larger for PM2.5 compared to PM10 is due to the fact that none-exhaust emission is a smaller fraction of total particulate emissions for PM2.5 compared to PM10. These estimates are lower than estimated in the Mid-term report since assumptions of the Mid-term report had relatively older vehicles and higher emission factors in the vehicle fleet than in the updated version, and the assumptions about the car fleet and traffic are also different.
The average effect in 2015 is only about 0.1 ?g/m3 and even less in 2020. This is expected as the low emission zone corresponds to an earlier introduction of Euro standards for heavy-duty vehicles than otherwise would have taken place and this effect will level off in time.
Although reduction of NOx emissions is not the primary objective of the low emission zone, these emissions are reduced due to a shift in emission classes of the heavy-duty vehicles. For H.C. Andersens Boulevard, NOx emissions are reduced by about 17% for smaller trucks (32t), 8% for larger trucks (>32t) and 40% for buses due to the low emission zone in 2010 due to a shift from older to newer trucks and buses. Total NOx emission from heavy-duty vehicles is reduced by 25%. The total reduction in NOx emissions is 8% when considering all vehicle categories. This is slightly lower than estimated in the Mid-term report due to the same reasons as stated for particle emissions. The reduction of NOx emissions of 40% for buses is not only driven by the requirements of the low emission zone but also environmental requirements to urban bus services as part of public procurement. These may be minimum requirements for emission standards and additional incentives to use newer emission standards. It is not possible to separate the impact of the low emission zone requirements and the environmental requirements to bus services based on the existing data collected.
The effects of the low emission zone for NO2 concentrations were assessed for all the streets where air quality monitoring is carried out. The reduction was about 1 ?g/m3 for H.C. Andersens Boulevard and Jagtvej in Copenhagen, 4 ?g/m3 for Banegårdsvej in Aarhus, 2 ?g/m3 for Albanigade in Odense, and 3 ?g/m3 for Vesterbro in Aalborg. The percentage effect of the low emission zones in 2010 are reductions of 4% for H.C. Andersens Boulevard and 3% for Jagtvej in Copenhagen, 11% for Banegårdsvej in Aarhus, 4% for Albanigade in Odense, and 7% for Vesterbro in Aalborg. Differences are primarily due to different shares of heavy-duty vehicles.
The differences between with and without low emission zone is reduced to 1-2 ?g/m3 in 2015 and close to zero in 2020 for NO2 concentrations. The effect of a low emission zone corresponds to an accelerated introduction of newer Euro emission standards than otherwise would be the case. This effect diminishes in time. There is still a minor effect of the low emission zone in 2015 but in 2020 there is only a marginal difference between without and with the low emission zone.
An impact assessment of the low emission zone on for air quality has been carried out based on model calculations for 138 busy streets in the cities of Copenhagen and Frederiksberg, 55 streets in Aarhus, 40 streets in Odense, and 31 streets in Aalborg.
The effects of the low emission zones are summarized in Table 1 (se report page 22) for NO2. In Copenhagen the low emission zone reduces the number of exceedances of the NO2 limit value from 47 to 29 in 2010 out of 138 selected streets. In Aarhus the low emission zone reduces the number of exceedances from 20 to 11 out of 55 selected streets and in Odense from 1 to 0 exceedances out of 40 selected streets, and none exceedances are seen in Aalborg.
In 2015 the low emission zone reduces the number of exceedances from 8 to 6 and from 2 to 0 in Aarhus while there are no exceedances in Odense and Aalborg. These calculations include the effects of the low emission zone and also new regulation of taxis that requires all new taxis in 2011 to comply with the Euro 6 emission standard. There are no exceedances in 2020.
Estimation of the number of exceedances is subject to considerable uncertainty due to uncertainty in the model system and input data.
Compared to the Mid-term report, fewer exceedances are calculated in 2010 and 2015 due to the updated information about the vehicle fleet, emission factors, and traffic data, and further the assumption about constant traffic that all in all give slightly lower emissions.
There are not calculated any exceedances of the air quality limit values for PM 2.5 (25 ?g/m3 in 2015) and PM10 (40 ?g/m3 in 2005), see Table 2 (se report page 23).
