Rail workers are to stage a series of strikes in three separate disputes over issues including pay, pensions and jobs.
Members of the Rail, Maritime and Transport union will take industrial action against London Underground (LU), Transport for London (TfL) and the Heathrow Express in the coming weeks.
LU workers will walk out for 48 hours from 9pm on April 28 and again for three days from 9pm on May 5 in the long-running row over Tube ticket office closures.
The first two days of action will take place ahead of a May Day event in London in memory of former RMT leader Bob Crow, and Tony Benn, who died within days of each other last month.
RMT members at TfL, who work in admin roles, will strike for 48 hours from 9pm on April 28 in a dispute over pensions.
The union is also staging a strike at the Heathrow Express train service for 48 hours from 3am on April 29 in a row over jobs, pay and cuts.
The union said plans to reorganise the workforce to save £6m over the next five years threatened 201 jobs.
Acting general secretary Mick Cash said: “RMT does not buy for a moment the case for handing out savage cuts to Heathrow Express when Heathrow is generating hand-outs to shareholders of over £600m.”
Keith Greenfield, managing director of Heathrow Express, said: “We remain eager to continue our productive discussions with RMT union reps and we still hope they choose to resolve the dispute around the table rather than through damaging industrial action.
“A strike is not the answer. It will increase costs when we are trying to reduce them, taking us further away from what we need to do to secure our business for the future.
“However, we will not let it stop us providing an excellent service. We have a robust contingency plan that will enable us to run regular trains for as long as any industrial action lasts.”