Air conditioning coming soon to London’s Underground

London’s Underground is a marvel, yet it relatively cramped spaces — they don’t call it the Tube for nothing — means that temperatures can often rise down below even on a typically cool, damp British day.

London Mayor Boris Johnson today unveiled a new Underground train model, which for the first time will come with air conditioning.

The new trains are to debut on the Metropolitan line in 2010 and will get phased in on other lines up until 2015.

“I can assure passengers who will use them that we hope, rather than arriving at their destinations drenched in perspiration, they will emerge cool as cucumbers and ready to enjoy all that the capital offers,” Johnson tells the Associated Press.

Why the Metropolitan line first, you might ask? The plan is to gradually replace many of the existing subway cars, starting with the city’s oldest subway lines first.