Passengers on the London Underground will face a strike on Wednesday.
The talks have failed to prevent the Central Line workers' strike, and the unions have warned against further strikes and a "nationwide shutdown" in the run up to Christmas.
Which lines will be affected?
Central Line and Waterloo & City Line workers will leave at 00:01 GMT for 24 hours.
Transport for London (TfL) said both lines would have very little or no service all Wednesday. The normal services would resume on Thursday.
A scheduled 24-hour strike on the Piccadilly Line, scheduled to start at 12:00, was canceled on Tuesday afternoon.
The Rail, Maritime and Transport union (RMT) said it had discontinued the action after talks.
Why are the workers striking?
Members of the RMT union and the driver union Aslef quarrel over industrial relations disputes, including personnel and working conditions.
RMT General Secretary Mick Cash said the union was "frustrated" because the Tube bosses "handled a whole host of issues".
He criticized the London Underground for a culture of "not hiring enough drivers to harass employees and expecting our members to pick up the pieces when service fails".
Cash said the members of the RMT had "made it clear that they have enough and are willing to fight for respect and justice in the workplace."
Finn Brennan, organizer of Aslef on the London Underground, said the union demands "a rapid change in the approach of management working within existing arrangements rather than trying to circumvent or reinterpret it".
He added, "The issues underlying this dispute – fair treatment at work and adherence to agreements – are not confined to just a few areas."
TfL said Aslef demanded the reinstatement of a Central Line driver who "was fired for a serious security breach after deliberately opening the doors of a train in a tunnel."
How does it affect passengers?
The strikes will cause peak hours in the morning and evening.
TfL said the services would be running normally on other subway lines, but warned that the connecting stations on the affected routes would be "much busier than usual".
Holborn Station is expected to close and TfL warns that some stations need to be closed temporarily to avoid overcrowding.
TfL will be driving additional buses during the strike, but the roads will be "busier than usual".
What does Transport for London say?
Nick Dent, Director of London Underground Line Operations, said the RMT and Aslef strike action was "totally unjustified".
"Our commitment to the safety of our customers and employees is absolute and we will never compromise," he added.
He has previously urged unions to "stop this completely unnecessary strike action that will only bother our customers."
Could there be more strikes?
Mr. Brennan has warned that if "TfL does not make the changes that union members want," there will be a "nationwide shutdown ahead of Christmas".
He said the Aslef Executive Committee would "discuss resolutions of our branches in the Hammersmith and City and Northern lines, calling for a vote that other branches should follow".
"Leaders at Transport for London need to recognize and address the seriousness of the problems of industrial relations in the London Underground," he added.
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