RMT union members oppose the voluntary introduction of a four-day working week with condensed hours.
Members of the Rail, Maritime and Transport Union walked out on Thursday for a second day of strike action.
Members of the Rail, Maritime and Transport (RMT) Union are due to walk out again on Thursday from 00:01 BST.
Transport for London apologises as commuters face another planned walkout on Thursday.
Members of the RMT union are on strike on Tuesday in a row over working hours, with further action planned for Thursday.
Drivers from the Rail, Maritime and Transport union are due to walk out on Tuesday and Thursday.
The Rail, Maritime and Transport (RMT) union calls off a series of 24-hour strikes starting on Tuesday.
The RMT union says transport workers are being assaulted on a daily basis and more action is needed.
RMT members are walking out in a dispute over proposed changes to their working week.
