Why are black cabs being tested in the Arctic Circle?
A brand new design for London's black taxi has been put through its paces in a hostile - and very clean - environment.
It's hoped this update will reduce pollution from the famous fleet of 23,000 vehicles.
Transport correspondent Richard Westcott reports.
So I Can Breathe
A week of coverage by BBC News looking at ways to cut air pollution.
- From the section UK