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Indicator Assessment

Exceedances of air quality objectives due to traffic

Indicator Assessment
Prod-ID: IND-106-en
  Also known as: TERM 004
Published 30 Oct 2008 Last modified 11 May 2021
12 min read
This is an old version, kept for reference only.

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This page was archived on 10 Feb 2021 with reason: Other (Discontinued indicator)
In 2005 road transport was the largest contributor to NOx emissions in Europe and the third largest for primary PM10. The data analysed from selected stations in major urban agglomerations, indicate that during the period 1999-2005 mean values of NO2 concentrations at road traffic stations remain relatively stable (trend is smaller than the statistical uncertainty on estimate) whereas an increase is observed in the maximum observed concentrations after 2003. The background concentrations remain relatively stable throughout the period 1999-2005. During 1999-2005, the maximum NO2 concentration at traffic stations is observed in London, whereas the maximum background concentration is observed in Paris. For PM10, a slight increase was observed in 2003 in the maximum background concentrations, but these have followed a slightly downward trend since. In 2005 a slight reduction is also observed in the maximum concentrations at traffic stations. Throughout the period 2002-2005, mean traffic and mean background concentrations remain relatively stable. The maximum traffic value during 2002-2005 is observed in Rome, whereas the maximum background concentration is observed in Prague for the period 2002-2004 and in Bratislava for 2005. Overall, the decrease in emissions does not appear to have a statistically significant influence on the air quality and the increase in the number of vehicles is off-setting the technological and fuel quality improvements.

TERM04 NO2 mean and maximum values of annual averages for traffic and urban background stations

Note: Station pairs from capital cities were preferred, but when not available the next largest city for which data was available was chosen

Data source:

AirBase

TERM04 PM10 mean and maximum values of annual averages for traffic and urban background stations

Note: Station pairs from capital cities were preferred, but when not available the next largest city for which data was available was chosen

Data source:

AirBase

  • NOx

NOx emissions from road transport decreased by 38 % in EEA member countries, 24 % in the 12 new member states and 42 % in EU-15 between 1990 and 2005. This was mainly due to the introduction of catalysers on new cars. Increasing road travel and increasing number of vehicles has partly offset reductions achieved by emission abatement. Even though emissions have decreased, in 2005 road transport still contributed 39 % to the total emissions in EEA member countries, 37 % in the 12 new member states and 40 % in EU-15 countries. The difference between average yearly traffic and background concentrations varies greatly from city to city, but overall higher values are observed at the traffic stations, indicating that traffic contributes significantly to NO2 concentrations in urban areas. Higher traffic concentrations are systematically not observed for the city of Athens. Due to the lack of other urban background station measurements and additional site-specific data, it is not possible to analyse this inverse trend any further. Overall, the differences between traffic and urban background are very large in some cases (reaching up to 72 mg /m3 in London in 2005), especially in comparison to the annual limit value of 40 mg /m3. The traffic-background difference appears to be generally quite stable in most cities.In Bratislava the difference has fluctuated more than in most cities between 1996-2005 and after an increase in 2002 (due to the high concentrations measured at the traffic station) a steady decrease is been observed in recent years. A decreasing trend is also observed in Berlin in recent years, but the high traffic concentration in 2005 offset this trend. A steadily decreasing trend is observed between 2003-2005 in Vilnius due to the reduction in traffic concentrations. In London a steadily increasing trend has been observed since 2002, due to the very large concentrations measured and the traffic station of Marylebone Rd.

Overall, the annual limit value is exceeded at traffic stations in almost all cities and the largest exceedances are observed in large urban agglomerations such as Bucurest, Budapest, London, Rome, Paris, Krakow, Madrid and Berlin (in that order).

The daily variation of NO2 concentrations across selected traffic and background stations indicates significantly higher concentrations at traffic compared to background stations, verifying the influence of road traffic. Another indication of the significant influence of traffic on the concentrations measured are the two peaks observed during the day, corresponding to the peak traffic hours which vary from city to city depending on the office and shopping hours. These appear more or less pronounced, depending on whether the city centre (where the traffic stations are located) attracts traffic throughout the day (e.g. Rome and London) and suffer round the clock congestion, or only during office hours like Bratislava and Madrid which have pronounced peak hours. Overall, significant exceedances of the hourly limit value are only observed in Bucurest, Budapest and London.

Finally, the 'Sunday effect' for NO2 (lower concentrations due to less traffic) is present in most background stations, but significant in traffic stations and also the concentrations observed over the week are generally lower at background stations, verifying once more the traffic influence.

  • PM10

Primary and secondary emissions of PM10 decreased by 38 % in EEA member states, 30 % in the 12 new member states, and 42 % in EU-15 countries between 1990 and 2005. The emission reductions were mainly due to abatement measures including fuel switching and the increased penetration of catalytic converters, since the application of abatement techniques to reduce precursor emissions often reduces the primary particle emissions also. However, road transport still contributes significantly to total primary and secondary emissions in 2005, 22 % in EEA member states, 15 % in the 12 new member states, and 26 % in EU-15 countries and the overall increase in road travel and number of vehicles has partly offset reductions achieved by emission abatement.

Data availability for urban areas across Europe is limited, since it only became mandatory to monitor PM10 concentrations from 2001 onwards. The difference between average yearly traffic and background concentrations varies from city to city, though not as much as for NO2. Higher values are almost always observed at traffic stations (with the exception of Reykjavik in 2003 and 2004, Bratislava in 2003, Prague in 2004 and Amsterdam in 2005), indicating that traffic contributes significantly to PM10 concentrations in urban areas. The traffic-background difference appears to be generally quite stable in the last few years in Helsinki, Copenhagen and London, whereas a decreasing trend is observed in Vilnius, Tallinn, Bucurest, and Rome. An increasing trend was observed in London and Berlin until 2003 (clearly due to the increasing traffic concentrations), though in 2005 in London the difference appears to have stabilised. In Berlin in 2004 the difference decreased due to a significant decrease of the traffic concentration, but increased again in 2005 for the same reason. In Krakow the limited data suggest that there is an increase in the difference between traffic and background concentrations due to the increase in traffic concentrations.

Concentrations measured an traffic stations in Vienna, Berlin, Madrid, Athens, Krakow and Bratislava all show an increase of more than 4 mg /m3 between 2004 and 2005. During the same period in Brussels, Budapest, Rome, Vilnius, Amsterdam and Bucurest a decrease of PM10 traffic concentrations is observed, whereas in 7 cities the trend is more or less stable. Overall, in 2005 the annual limit value of 40 mg /m3 was exceeded at traffic stations across a number of large cities in Europe.

The daily variation of PM10 concentrations across traffic and background stations shows that significantly higher concentrations are observed at traffic compared to background stations, verifying the influence of road traffic. The two peaks related to the traffic peak hours are again observed, though, similarly to NO2, in London increased traffic is observed throughout the day (see explanation in NO2 assessment).

The 'Sunday effect' for PM10 (lower concentrations due to less traffic) is present at background stations but significant at traffic stations and also the concentrations observed over the week are lower at background stations, verifying once more the traffic influence. The daily limit value is exceeded on most weekdays in Krakow and significant exceedances are also observed in Rome, London, and Bratislava (see accompanying excel sheet for details).

Supporting information

Indicator definition

This indicator compares concentrations of pollutants at background stations to those at traffic stations. This comparison provides an estimate of the increased levels of air pollution to which the population is exposed in areas with increased road traffic. It also provides a measure of the impact of the technical and non-technical measures adopted to reduce the road transport sector's contribution to observed concentrations. 

The indicator makes use of the data submitted to Airbase. Data permitting, pan-European coverage is attempted and the indicator focuses on selected station pairs (traffic and urban background stations) from capital cities across Europe. Where data in capital cities are not available, the next largest city is chosen.

Units

The units used in this indicator are the average yearly, daily and weekly variations of the concentrations at traffic and urban background stations, measured in micrograms per cubic metre (mg/m3).


 

Policy context and targets

Context description

This indicator provides information relevant for current European air quality legislation related to the setting of national emission targets (National Emission Ceiling Directive 2001/81/EC), the reduction of transport related emissions (discussed in detail in TERM 34) and the protection of human health from harmful air pollutant levels (Directives 1999/30/EC for sulphur dioxide, nitrogen dioxide and particulate matter and 2002/3/EC for ozone, both discussed in detail in CSI 004). The Directive on ambient air quality and cleaner air for Europe (Directive 2008/50/EC) also sets target and limit values for PM2.5 (particulate matter that passes through a size-selective inlet with a 50 % efficiency cut-off at 2.5 micrometres aerodynamic diameter), since 2010.

Targets

EU limit values for concentrations of nitrogen dioxide in ambient air

Both limit values had to be met by 1 January 2010:

  • In the Council Directive 1999/30/EC (section 1 of Annex II), an annual mean limit value for nitrogen dioxide of 40 mg NO2/m3 has been set for the protection of human health.
  • An hourly limit value of 200 mg NO2/m3, not to be exceeded more than 18 times per calendar year, has also been set.

 

EU limit values for concentrations of PM10 in ambient air

Both limit values had to be met by 1 January 2005:

  • a limit value for PM10 of 50 mg/m3 (24 hour average, i.e. daily), not to be exceeded more than 35 times per calendar year, has been set for the protection of human health in Council Directive 1999/30/EC (Annex III).
  • an annual average limit value of 40 mg/m3 has also been set.

 

EU limit values for concentrations of other pollutants:

- sulphur dioxide

Two limit values have been set for the protection of human health. Both limit values had to be met by 1 January 2005

  • a limit value of 125 mg SO2/m3, as a daily average not to be exceeded more than three times per calendar year, has been set for the protection of human health in the adopted Daughter Directive 1999/30/EC, Section I of Annex I.
  • an hourly limit value for the protection of human health has been set at 350 mg.

 

- ozone 

A combined ozone and acidification abatement strategy has been developed by the European Commission, resulting in a new Ozone Daughter Directive (2002/3/EC) and a National Emission Ceiling Directive (2001/81/EC). In this legislation, target values for ozone levels and for precursor emissions have been set.

  • The Ozone Daughter Directive sets a target value for the protection of human health of 120 mg O3/m3, as a maximum daily 8 hour mean, not to be exceeded on more than 25 days per calendar year, averaged over three years. This target should be met in 2010.
  • The Ozone Daughter Directive has also set a long-term objective of 120 mg O3/m3, as a maximum daily 8 hour average not to be exceeded on any day within a calendar year.

Related policy documents

  • COM(2001) 245 final. The Clean Air for Europe (CAFE).
    The Clean Air for Europe (CAFE) Programme: Towards a Thematic Strategy for Air Quality COM(2001) 245 final
  • Council Directive 96/62/EC of 27 September 1996
    Council Directive 96/62/EC of 27 September 1996 on ambient air quality assessment and management.
  • Council Directive 1999/30/EC of 22 April 1999
    Council Directive 1999/30/EC of 22 April 1999 Relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in ambient air
  • Directive 2001/81/EC, national emission ceilings
    Directive 2001/81/EC, on nation al emissions ceilings (NECD) for certain atmospheric pollutants. Emission reduction targets for the new EU10 Member States have been specified in the Treaty of Accession to the European Union 2003  [The Treaty of Accession 2003 of the Czech Republic, Estonia, Cyprus, Latvia, Lithuania, Hungary, Malta, Poland, Slovenia and Slovakia. AA2003/ACT/Annex II/en 2072] in order that they can comply with the NECD.
  • Directive 2002/3/ EC...ozone in ambient air
    Directive 2002/3/ EC of the European Parliament and of the Council of 12 February 2002 relating to ozone in ambient air
  • Directive 2008/50/EC, air quality
    Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe.
 

Methodology

Methodology for indicator calculation

Concentrations
Data submitted to Airbase have been used. The average diurnal variation was obtained by averaging each hour of the hourly data available at the selected measurement station. Average weekly variation was obtained by averaging the daily average for each day of the week (hourly or average daily data were used, depending on data availability) at the selected measurement station. Average yearly data were obtained from average hourly or average daily data, whichever were available at the selected measurement station (see data availability table for details). For all of the above, data gaps were not filled in.

Methodology for gap filling

No gap-filling is applied for this indicator, however, the databases and spreadsheets used for the production of the indicator contain gap-filled values.

Methodology references

No methodology references available.

 

Uncertainties

Methodology uncertainty

Air quality data are officially submitted. It is assumed that data have been validated by the national data supplier. Station characteristics and representativeness are often insufficiently documented. The data are thought to be representative for the urban population in each city. Locally, (at the city level) the indicator is subject to year-on-year variations due to meteorological variability.

Data sets uncertainty

  • Strengths and weaknesses (at data level): data officially reported by the countries to Airbase are used, however, the data reported across countries vary in quantity. Also, the station characterisation (urban background or traffic) is difficult to compare across countries. 
  • Reliability, accuracy, robustness, uncertainty (at data level): Uncertainties are discussed separately for each graph. The data quality cannot be commented upon, since the data are reported by the individual countries, but data availability is sometimes low and does not allow for robust conclusions/intercomparisons (see data availability table for details). The main problem is the lack of data and not the actual quality of the data available.

Rationale uncertainty

No uncertainty has been specified

Data sources

Other info

DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • TERM 004
Frequency of updates
Updates are scheduled once per year
EEA Contact Info info@eea.europa.eu

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Geographic coverage

Dates

Topics

Tags

Filed under:
Filed under: transport
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