Transport for London (TfL) is looking at the feasibility of deploying 3G and 4G at stations on the London Underground but claims the technology can't be rolled out to passengers without investment from the private sector.

TfL CIO Steve Townsend told Techworld that he wants to see the connectivity on London Underground improved, adding that the organisation is testing a number of communication technologies, including on-train Wi-Fi.

“We have some trials working successfully in those spaces,” said Townsend. “It’s a question of working out how much money you now expend.”

Townsend said that it would be unfair to take public money away from railway upgrades, such as the one currently happening on the Bakerloo Line, in order to fund advances in connectivity.

“How far away [deployments are] is difficult to tell because that’s all based around investment,” he added. “It depends how keen the private sector is to help out a public sector organisation.”

Several other underground railways already offer 3G and 4G connectivity, including Hong Kong's MTR and Seoul's Metropolitan Subway. Meanwhile, New York, Paris and Sydney have all announced that they too will be rolling out 3G and 4G services over the next year or two. 

Townsend revealed that there are several other issues, in addition to investment, that need to be taken into account when rolling out any new technology on the world’s oldest underground railway.

“The Underground, whilst we keep it very clean and very safe, it’s still quite a hostile environment for modern technology,” he said. “There’s lots of human skin down there that builds up and obviously gets clogged up. So it’s not just a question of taking an access point or a transformer or an amplifier and putting it down there. We need to make sure it will work. Some of the technology handles it quite well and some of it doesn’t.

“The service model is also something we have to look at. How sustainable would those forms of technology be. Once it’s there people expect it to just work. They also want it there all the time.”

Last year TfL started rolling out Wi-Fi to stations on the London Underground network with the help of Virgin Media. There are now 120 stations out of a possible 270 that offer Wi-Fi.

A TfL spokesperson said: “We know that Wi-Fi on the underground has been hugely successful. In the first six months of Wi-Fi on the underground, there were 100 million user sessions with an average of 800,000 user sessions per day.”