10 years before air conditioning arrives

Air conditioning will be fitted on Tube trains but not for another 10 years.

Engineers have been working on ways to put cooling units on trains but have encountered problems with deep-level lines.

On the Northern, Bakerloo, Central, Victoria, Jubilee and Piccadilly lines, sources say, there is not enough room to fit the bulky equipment.

Most of the Underground system dates from Victorian and Edwardian eras when cooling systems were not considered.

There are plans to fit air conditioning to larger trains which use the wider tunnels - such as the District, Circle, Metropolitan and East London line.

The new District line stock will get them first - but not until 2013.

The Jubilee line's new stock has on-train ventilation system - not full air conditioning - but "blowers" within the roof at least keep the air circulating. It is the best LU currently has to offer and could be extended to other deep-level lines.

Two years ago, after an incident when thousands of passengers were trapped on trains stranded in 100F temperatures, Ken Livingstone offered £10,000 to the first person to come up with a workable way to cool the Tube.

The Underground is conducting research into the problem.

But there are no air quality standards for the Tube and for humans there is no maximum temperature.