Drivers on the London Underground are set to stage a 24-hour stroke due to a dispute over working conditions.
The walkout is set to begin on 5 October and could cause travel chaos for the millions of commuters who use the Tube in the capital every day.
More than 88% of workers in the Aslef union voted in favour of the strike.
Finn Brennan, Aslef's organiser on London Underground, said: "Aslef members have voted by an 88% margin to take strike action in our dispute over the failure of LU to deliver on the commitments they made to improve work life balance as part of the 2015 pay settlement.
"As part of the settlement of the dispute over the introduction of Night Tube, LU agreed to introduce a mechanism to allow drivers to reduce the number of shifts they work, on a pro-rata basis, and 'new ways of working' to reduce the percentage of weekend shifts worked by July this year. They have repeatedly refused to make any detailed proposals to do so.
"For more than 18 months management have prevaricated, stalled and delayed. Deadlines have repeatedly been missed and promises broken while our detailed proposals to resolve these issues have been ignored.
"Our members' patience has finally been exhausted and our executive committee has announced strike action. As always, we are ready to meet at any time to try to find a solution, but it is long past time that LU management started to act to resolve this long running dispute."
Nigel Holness, London Underground's director of network operations, said: "We are committed to ensuring that our employees are able to maintain a good balance between their work and personal lives, and we have been working closely with the unions to explore new ways to achieve this.
"I encourage Aslef to continue working with us constructively rather than moving towards unnecessary strike action."