CO2 emissions
Carbon dioxide emissions from cars will obviously depend on mileage and fuel consumption, but different engines and fuels will also have an impact. Average CO2 emissions of new cars sold over the last three years have fallen as a result of the increase in diesels sold. Diesels have lower greenhouse gas emissions than equivalent petrol engines.

However, the average CO2 emissions of petrol cars have increased over the same period, possibly due to ‘opting out drivers’, and the same has happened to diesels. Drivers who opt out from company car schemes often choose more highly powered cars than they would have previously been allowed. Also, to meet the Euro IV standard, diesels have to be tuned to run slightly less efficiently in terms of CO2 emissions.

Since all cars have an official combined fuel consumption as well as official CO2 figures, it is now possible to estimate CO2 emissions in a simple linear fashion.

For instance if a fleet car uses 10% more fuel than the Euro combined official figure, then it can be assumed that the CO2 emissions will also be 10% higher than the official figure.

Scientifically this may not be very accurate, but it makes it possible to accurately measure the trend from one year to another, and to present the results in CO2 terms weighted according to the precise mix of vehicles in the fleet. A target can then be set to reduce CO2 emissions from the company car fleet by a certain percentage each year.

Widely recognised external benchmarks do not exist but this doesn’t matter. The most relevant benchmark to use is the base point at which a company first acquires sensible data.

The purpose of benchmarking
Benchmarking on its own won’t do anything. It can, however, be used to measure the success of a company’s environmental initiatives. For instance, if financial incentives are used to encourage employees to choose low emission vehicles, it should be possible to estimate fleet emissions before and after this policy was implemented.

Rupert Russell, is the publisher of www.comcar.co.uk, a specialist company car tax website.

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