by Chirag Trivedi BBC News Online, London

Temperatures on trains reach 30C

An idea imported from the gold mines of South Africa could stop commuters suffering sweltering heat on London's Tube network.

An Israeli firm says giant snow machines should be built above ground.

Avshalom Felber, President of IDE Technologies, said the snow made at street-level would be pumped through pipes into containers placed in train tunnels or at platform entrances.

Then as trains pass through it would create air currents causing cold air from the containers to circulate and cool passengers in stations.

The idea is one of 3,000 entries submitted to London Underground after mayor Ken Livingstone offered �100,000 for the best solution for cooling the Tube in July.

Mr Felber said the company had used similar technology to cool gold mines in South Africa.

He added that each snow making machine costs �3.8m and six of them would be need to cool the 14-mile long Circle Line, which has 27 stations.

COOL IDEAS Your ideas to cool the Tube

The entire network has 12 lines.

London Underground has long grappled with the problem of how to cool narrow tunnels - some built more than a century ago - which lie up to 60 metres below London's streets.

Temperatures regularly top 30C (90F) in the deep tunnels of the network, according to a survey conducted by Liberal Democrat shadow transport minister Tom Brake last summer.

If the rush-hour trains travelling through such temperatures were crammed with sheep - rather than sweating human commuters - such conditions would break European livestock regulations, Mr Brake said.

Global entries

During this year's exceptionally hot summer, signs have been put up in stations warning passengers of the hazards of travelling in such temperatures and what they should do if they begin to feel unwell.

BBC News Online asked for readers' ideas for cooling the Tube and received more than 2,000 ideas, which were sent on to Ken Livingstone.

Among them were handing out ice lollies, turning the tube into a Venetian-style oasis and putting up posters of snowmen to make people think of winter.

A spokesman for London Underground said: "We have received over 3,000 entries from all over the globe.

"But we cannot comment on specific ideas as this would prejudice them and subsequent entries."