Carfolio Calculated CO2

Version: 1.0
Released: 07 October, 2007

Background

CO2 emissions data is now required to be published by motor manufacturers wishing to sell vehicles throughout Europe, as well as in a number of different markets. A number of laws and levies are today based on these figures, and they are considered important to some people looking at making purchasing decisions. Not all cars that are still regularly driven have their official CO2 data declared, as they were sold before the requirement for such declarations came into effect. The Carfolio Calculated Carbon Dioxide figure as an attempt to find a reasonable calculated CO2 emissions figure for those vehicles.

Derivation

Official CO2 figures are calculated from the official fuel consumption figure for a specific model, as tested by the manufacturer in a strictly controlled environment, mandated by EU Directive 80/1268/EEC, as last amended by 2004/3/EC[1]. For vehicles tested under the previous EU Directive 80/1268/EEC legislation [2], deriving the CO2 value is achieved in exactly the same way, but the fuel consumption test itself measures different data.

In order to derive a figure that is useful in comparison to the figures quoted under the current amended EU Directive, the fuel consumption figures need to be weighted to bring the results in line with today's testing regimen. The current consumption figures measure urban and extra-urban consumption, and then provide a weighted average of the two figures to come up with an overall figure. The official CO2 data quoted is a derived value from this overall figure.

Previously, the consumption figures quoted officially were for a steady 90 km/h, a steady 120 km/h and an urban cycle. The older urban cycle figure was obtained in quite different conditions, so it's not a like-for-like comparison with current figures either. Weighting these figures to provide an estimated "overall" figure - something not previously laid down in the legislation - enables the estimation of a similar CO2 value for cars that were subject to data released under the old directive.

Disclaimer

Whilst the above is a reasonable (in our opinion) method to retrospectively provide an equivalent contemporary CO2 emissions value for certain cars, it is certainly not endorsed by any legal body or manufacturer. It is an entirely derived method and is presented as an estimation. It is merely of academic interest, and has not been physically tested. It is provided for comparison only. If a manufacturer supplies a CO2 figure for a vehicle, that figure should be taken as the reference value.

References

  1.  VCAcarfueldata.org.uk - Fuel Consumption Testing Scheme
  2.  Council Directive 80/1268/EEC of 16 December 1980 on the approximation of the laws of the Member States relating to the fuel consumption of motor vehicles

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