Hundreds of tube drivers are set to walk across two days of planned strikes in London.
Commuters are set to face disruption across at least four Underground lines with two 24-hour stoppages scheduled for Tuesday and Thursday.
Drivers with the RMT union previously went on strike in April in a dispute over a four-day working week.
A strike planned for May 19 and 21 was called off at the eleventh hour following progress in talks.
TfL has insisted any such schedule would be voluntary and would not result in a reduction of contracted hours.
Sign up for all of the latest stories
Start your day informed with Metro’s News Updates newsletter or get Breaking News alerts the moment it happens.
Tube services will be heavily disrupted on strike days, which will run from 00.01 to 23.59 on Tuesday, June 2, and then the same hours on Thursday, June 4.
On those days, no service at all is expected on the Circle line or the Piccadilly line.
There will also be no trains on the Metropolitan line between Baker Street and Aldgate, and on the Central line between White City and Liverpool Street.
While other lines including Overground and Elizabeth Line will operate as usual, service levels will vary with trains starting later and finishing earlier than usual, with customers advised to complete journeys before 9pm on both days.
A normal service is expected to run on Monday, Wednesday and Friday, TfL has said.
TfL chief operating officer Claire Mann said the transport authority was hoping to pilot proposals for a four-day week on the Bakerloo line, which it said had support from ‘a significant number’ of drivers.
She said: ‘We are disappointed to see the RMT continue with this industrial action.
‘We still believe that the points they have raised can be worked out in time, through more detailed discussions and we are continuing to talk to the union’s representatives to find a way to avoid disruption to London.
‘We urge the RMT to work with us so we can resolve this dispute. In the meantime, we are asking customers to check before they travel and allow plenty of extra time for their journeys.’
RMT confirmed this week that strikes would go ahead, citing concerns the proposed four-day week could lead to ‘fatigue, longer shifts and reduced flexibility’.
Get in touch with our news team by emailing us at webnews@metro.co.uk.
For more stories like this, check our news page.