BBC: Reducing pollution from cars has been cheaper and easier than UN experts thought, a draft report says.
The UN's climate panel has admitted it underestimated the huge gains in weight and fuel efficiency achieved by car manufacturers.
But the panel says all the improvements will be swamped by the future growth in global traffic.
That is unless governments improve public transport, tax motorists and plan cities for walking and cycling.
The report, seen by BBC News, warns that transport will...