Disruption continued on Wednesday, with a knock-on impact on services expected on Friday as well.
A London Underground worker has said the Tube strikes are “very much in passengers’ interests”.
RMT union member Daniel Randall was on the picket line at Oxford Circus Tube station, where he works, on Thursday.
The 35-year-old told the PA news agency: “I’m on strike today with around 10,000 of my workmates across London Underground.
“We’re striking for three reasons. Firstly, to protect jobs, because London Underground has announced plans to cut 600 positions from Tube stations across London… and we’re also striking to protect our pension arrangements, because they’re currently under review and the company’s made it clear that they want to save money by reforming our pension arrangements.
“We’re striking to protect our conditions, because they’re under review.”
He added: “We’re standing up for a properly funded, properly staffed Tube system, and we feel that’s very much in passengers’ interest as well as our interests” since fewer workers would mean “a lower quality and less safe service for passengers”.
Transport for London (TfL) has advised people to work from home if they can on Thursday, saying there are likely to be no Tube services.
There were huge queues at bus and taxi ranks as people switched to other forms of public transport to get to work.