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How CO2 Emissions Are Measured

By: Kevin Dowling BA (IMC) - Updated: 31 Aug 2010 | comments*Discuss
Co2 Carbon Dioxide Emissions Levels

Carbon dioxide, also known as CO2, is widely considered as one of the most dangerous of ‘greenhouse’ gases, responsible for changing the intensity and regularity of weather events such as storms, droughts and floods. But how are CO2 levels tested by car manufacturers, and are they fair with their testing?

Working towards a Cleaner Environment

Since the 1980s, governments have taken steps to reduce the level of CO2 emissions, and one of the most significant steps they have taken has been to reduce the emissions of motor vehicles.

Every vehicle registered in the UK must be taxed if it is used or kept on a public road. The amount of annual Road Tax that a motorist must pay depends on the engine size of the vehicle and also is CO2 emission levels.

These are the emissions that are produced by the engine and expelled into the atmosphere through the car’s exhaust pipe.

So why do CO2 test results matter so much?

CO2 levels can have a big impact on the price you pay for Road Tax. Just 1 g/km can be the difference between a £35 tax bill and a £120 one. For company car drivers, the difference are amplified, and can have a heavy impact on your tax bill, making a high emittance car very costly indeed.

Road Tax Legislation

If your vehicle was registered after 2001, then there are a number of different Road Tax bands based on the fuel type of the car (petrol or diesel) and the CO2 emission levels for that make and model of car.

The 2008 Budget, however, included the announcement that from 2010 onwards, a new road tax rate would become applicable for cars in the first year of registration. But just how are these CO2 emissions measured?

Less than Impartial Testing?

Anyone choosing a new car could be forgiven for thinking that the official CO2 tests carried out to determine a car's emissions output are both impartial and accurately measured. This, however, is not necessarily the case. The emissions-testing procedure is less impartial than you may think.

For a start, the CO2 tests are carried out by the car manufacturers themselves. They each use their own testing facilities and equipment to measure emissions output.

Each car is examined for fuel consumption and exhaust emissions, with the driver on a ‘rolling road’ asked to follow a set of instructions (changing gears, speeding up, braking and so on).

These results are turned into data which is then applied for each car within the range.

Often, the car will be tested in one country and these results will apply across every country in which the car is sold. Furthermore, car manufacturers can resubmit their cars for further testing if the first results were worse then they had hoped for.

Clearly whilst emissions testing is a positive thing for the environment, car manufacturers are still able to use their own testing procedures to help ensure they get the results they want. Isn't it time for worldwide state controlled emissions testing procedures?

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