Transport for London are operating a limited service on most tube lines, but they advise to check before you travel.
Union leaders were under pressure tonight to call off the strike after it emerged new peace talks would take place on Friday.
Bob Crow has told ITV News that he does not use ticket offices at London Underground stations.
The Federation of Small Businesses claims that the recent tube strike cost companies in the capital £600 million in lost working hours, business and productivity.
Members of the FSB lost on average £1,297 during the last tube strike.
– Sue Terpilowski, London Policy Chairman, Federation of Small Businesses
The Capital is one of the most expensive places in the world to do business - all sides of the ongoing dispute need to understand that damaging small businesses in this way leads to a decline in confidence and turnover, and that can mean jobs and capital investment at risk. We urge all sides to find a quick resolution as the average business can ill afford to lose over £2,500 in a two week period.
Talks aimed at averting a second Tube strike resume today. Union members staged a 48-hour walkout last week and another is planned to start tomorrow unless a row over ticket office closures is resolved.
Mike Brown, Managing Director of London Underground told ITV London, "I'm hoping we can meet in the middle. But we've got to hear from them - saying no no no or storming out of meetings clearly doesn't allow for that dialogue."
Unions and tube bosses are due to meet at conciliation service ACAS tomorrow.
– ACAS Spokesperson
Following seven days of formal talks at Acas, it was not possible to break the deadlock and we felt it would be helpful to have a period of reflection during which the parties had the opportunity to consider their positions and look at fresh ideas to reach an agreement.
It was clear that an Acas meeting today would not have prevented the second day of strike action from going ahead. We are now concentrating on seeing whether next week's strike dates can be headed off. We have been in contact with the parties since the last Acas meeting.
More than 40 stations are closed this evening. For full details before you travel, visit Transport for London's website.
There is a good service running on the Northern line this afternoon as well as the DLR and the Overground.
The Circle and Waterloo & City lines are closed.
All other lines are running a special service.
Check the TfL website before you travel.
More commuters have braved the tube strike this morning with 91% of regular Oyster customers travelling in London. This compares with 86% who used their Oyster cards yesterday.
Reporting on how the Underground has performed so far today, Transport for London said:
- Services operating on 9 of the 11 lines
- Nearly 75 per cent of stations open
- Some 91 per cent of regular Oyster customers have been travelling in London this morning
- Barclays Cycle Hire journeys up 50 per cent for the second day
LU managing director Mike Brown said:
"Many thousands of LU and TfL staff are working hard again today to keep customers informed and to keep London moving and open for business.
"I am grateful to our customers for their patience, and we will be doing everything we can to run as many services as possible. I'm pleased that more staff have come to work today than yesterday.
"My message to the leadership of the RMT and TSSA is 'why wait to sit down with us until Friday?'. They should do the right thing, meet us at Acas today, and suspend this completely unnecessary strike.
Many commuters switched to using the capital's bike hire scheme to get to and from work.
Barclays Cycle Hire journeys were up by 50% yesterday, with almost 30,000 hires.
The same trend has been seen today, with over 11,000 hires by 10am.