Plans to trial mobile phone use on London's tube network have not been implemented due to high costs, it has been revealed.
In March 2007, Transport for London (TfL) called for schemes to be submitted for a six-month trial of using mobile phones on the Waterloo & City line to see if it would be cost effective.
A TfL spokeswoman told silicon.com that none of the three proposals that has been received were "commercially credible".
"London Underground tendered for a trial of mobile phones on the Waterloo and City line but the market has yet to provide us with a credible proposal for enabling mobile-phone use on the Tube," she said.
"While it is technically possible to deploy mobile-phone and data-wireless solutions on the deep-level Underground tunnels and stations, the unique nature and environment of the Tube mean that project costs would be prohibitively high at this time."
TfL also said there are currently no active plans to trial or roll out mobile phone use on London Underground.
Last year mobile network O2 and telecoms firm Arqiva announced they has installed radio network equipment in Glasgow's underground, which allows passengers to use their mobile phones during their journeys.