Cars raise various ethical issues. They account for around a fifth of the UK's greenhouse gases, with a typical vehicle producing its own weight in CO2 for every 6,000 miles driven. Moreover, car emissions include a cocktail of noxious fumes which, in the UK alone, contributes to around 25,000 premature deaths each year.

And that's not to mention road accidents (more Brits have died on roads since 1945 than were killed in World War II) and the questionable ethical records of many oil and car companies.

You can, alarmingly, watch the environmental and human costs of our driving increasing in real time at www.roadsafety.co.uk.

Your choice of car, and how you drive it, can have a big impact on your carbon footprint. Duncan Clark explains how you can limit the damage you cause when you take to the road.