The association, part pressure group and part breakdown service, obtained performance details from 21 car makers. It gave models a green ranking based on seven factors: engine size, horsepower, two measures of fuel consumption (urban cycle and steady 56mph), noise, top speed and acceleration. The latter two were used as 'indicators of aggression'.
The lower a car's top speed and acceleration and the smaller its engine size and horsepower, the higher a score it gained. Chris Bowers, who heads the association, said: 'There is no such thing as a 'green' car, but clearly some cars do more damage to the environment than others.'
Cars with smaller engines and lower horsepower tend to burn less fuel and produce less pollution. But Gavin Green, editor in chief of Car magazine, said fuel consumption alone was a much better measure. 'There are plenty of cars with slightly larger engines which are more fuel efficient than some of the smaller engined types,' he said.
The points system did not take into account emissions of the three key traffic pollutants - carbon monoxide, hydrocarbons and oxides of nitrogen - which produce urban smog and threaten human health. Catalytic converters remove the bulk of these gases.
Mr Bowers said emission levels were closely linked to fuel consumption, which was taken into account. This was also a good measure of emissions of carbon dioxide, the most important of the 'greenhouse gases'.
Subaru's Vivio has four-wheel drive, a 658cc engine and a top speed of 83mph. In urban driving it consumes 6.7 litres per 100km, (42 miles per gallon) compared to 17.1 litres per 100km (16.5 mpg) for the Porsche Carrera.
The remainder of the guide's top ten were, in order: the Toyota Starlet, the Fiat Panda, the Vauxhall Nova and Cavalier diesels, the Daihatsu Charade, the Vauxhall Nova with 1.2 litre petrol engine, and the Fiat Uno. Next to last came the Jaguar XJ6.
ETA Car Buyer's Guide; The Old Post House, Heath Road, Weybridge KT13 8RS; pounds 2.
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