Workers on the London Underground are striking for a second day on Thursday in protest at ticket office closures and job cuts.

The strike, the first of two planned 48-hour stoppages, began late on Tuesday.

Transport for London (TfL), which operates the city's transport network, reported only one underground line was running normally at rush hour on Thusday. The remaining 10 were either closed or running a reduced service, it said.

Millions of commuters have been forced to seek alternative forms of transport, with many swapping to overcrowded buses or mainline trains. Others have opted to cycle, with a 50 percent increase reported in the use of London's bicycle hire scheme, dubbed "Boris bikes", after mayor Boris Johnson.

The London Chamber of Commerce and Industry has estimated that the industrial action will cost the city's economy 50 million pounds ($80 million) a day.

Cost of modernization

Wednesday saw similar travel chaos, with many commuters unable to reach their places of work as Underground services were reduced by around 70 percent.

The National Union of Rail, Maritime and Transport workers (RMT) and the Transport Salaried Staffs' Association (TSSA) called the strike to protest against job losses and a proposal to close manned ticket offices.

The changes are part of the planned modernization of the 151-year-old underground transport system. TfL claims the changes could save 50 million pounds a year.

Talks between the two main rail unions and TfL are scheduled to resume on Friday in a bid to avert a second 48-hour stoppage planned from February 11 to February 14.