Transport contribution to air quality

Indicator Fact Sheet (Deprecated)
Prod-ID: IND-106-en
Also known as: TERM 004
Topics: , ,

Assessment made on  01 Jun 2006

Generic metadata



DPSIR: Impact


Indicator codes
  • TERM 004

Policy issue:  Meet EU air quality standards set for protection of human health

Key messages

  • Road transport is the largest contributor to NOx emissions in Europe and the second largest for PM10. The data analysed from selected stations in major urban agglomerations, indicate that both mean and maximum values of NO2 concentrations at road traffic stations remain relatively stable (trend is smaller than the statistical uncertainty on estimate) during the period 1999-2002, though an increase is observed in the maximum observed concentrations in 2003 and 2004. The background concentrations remain relatively stable throughout the period 1999-2004. During the period 1999-2004, for NO2 the maximum traffic concentration is observed in London, whereas the maximum background concentration is observed in Paris. For PM10, although an increase is observed during the period 2001-2003 in both station types for the mean concentrations and the maximum background concentrations, a slight decrease is observed in 2004. The maximum concentration at traffic stations remains relatively steady during the same period. During the period 2002-2004 the maximum traffic value is observed in Rome, whereas the maximum background concentration is observed in Prague. 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.


Key assessment


NOx emissions from road transport decreased by 35 % in EEA32, 32 % in EU10 and 38 % in EU15 between 1990 and 2004 (see table 6). This was mainly due to the introduction of catalysers on new cars. Increasing road travel and increasing number of vehicles (see TERM 2004 32; EEA, 2003) has partly offset reductions achieved by emission abatement. Even though emissions have decreased, in 2004 road transport still contributed 40 % to the total emissions in EEA32 countries, 36 % in EU10 countries and 42 % in EU15 countries (see table 7). The difference between average yearly traffic and background concentrations (see fig. 3) 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 were systematically not observed for the city of Athens during the period 1996-2003, though in 2004 this difference was eliminated. 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.


Primary and secondary emissions of PM10 decreased by 36 % in EEA32 and EU10, and 39 % in EU15 countries between 1990 and 2004 (see table 6). 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 2004, 22 % in EEA32, 17 % in EU10, and 26 % in EU15 countries (see table 7) and the overall increase in road travel and number of vehicles (see TERM 2004 32; EEA, 2003) has partly offset reductions achieved by emission abatement.


Road transport emissions of sulphur dioxide have been reduced by 80 % between 1990 and 2004 in EEA32, 93 % in EU10 and 88 % in EU15 countries (see table 6). The emission reductions were mainly due to the considerable reductions in the sulphur content of automotive fuels over the period, which appears to have had an effect on the concentrations observed, despite the increasing traffic volumes (see TERM 2004 32; EEA 2003). However, in 2004 SO2 emissions from road transport only represent 2 % of the total emissions in all EEA32 countries (see table 7).


O3 concentrations across Europe depend on ozone precursor emissions, however the relationship is highly non-linear. Emissions of TOFP have been reduced between 1990 and 2004 by 49 % in EEA32, 41 % in EU10 and 54 % in EU15 countries (see table 6), but transport volumes have increased partly off-setting the effect of the emission reductions (see TERM 2004 32; EEA 2003).


Although in 2004 road transport contributes significantly to total emissions, 41 % in EEA32, 30 % in EU10 and 44 % in EU15 countries (see table 6), CO traffic and background concentrations showed very low values compared to the limit value (running 8-hour average concentration of 10 mg/m3 in 2005), hence it was not considered necessary to include this pollutant in the analysis. Moreover, a further reduction in CO emissions is expected, judging from the trend between 1990 and 2004, where a reduction of 60 % in EEA32 was observed. However, it should be noted that in some countries the change between 1990 and 2004 was significantly less than the overall average (e.g. only 17 % in the Czech Republic) and in some countries even an increase was observed (e.g. 97 % in Iceland and 13% in Turkey). Measurement data for Iceland show that concentrations at traffic stations are still very low compared to the limit value and the % increase in emissions is due to very low emissions in the reference year (1990). Data for Turkey is not available.

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