Personal transport accounts for nearly a third of the typical person's carbon footprint in the UK. Transport as a whole is the fastest growing major source of greenhouse gases. Compared to public transport such as bus or train travel, most cars are very inefficient - especially when only carrying 1 or 2 passengers.

Aviation is a huge problem from a climate change perspective. A molecule of a greenhouse gas is several times more powerful when emitted at flight level than at lower elevations.

Two people flying on a return trip between Europe and US produce 4 tonnes of CO2, which is almost half of a UK citizen's carbon footprint and what a typical US car generates each year.