Transport for London has warned commuters they will face four days of disruption on the Tube, should planned industrial action go ahead next week.
TfL has said tube services will be affected between Tuesday 25 and Friday 28 August, if two 24 hour stikes planned by three of the four Tube unions go ahead.
The first strike will run for 24 hours from 9pm on August 25, and the second will run for 24 hours from 9pm on the August 27.
The strikes are part of an ongoing dispute over plans to introduce 24 hour Tube services at weekends.
Members of the RMT, the biggest union, are set to take part, as are TSSA and Unite members.
Aslef, the union representing most Tube drivers, has suspended industrial action, saying it remains "optimistic" about further talks.
Staff on the bus network, DLR, London Overground, TfL Rail, tram, Emirates Air Line and River services will not be on strike.
A TfL spokesperson said: "These services will operate as normal but they will be much busier than usual, especially during peak hours, between Tuesday 25 and Friday 28 August.
"Roads and National Rail services and terminals will also be much busier.
"We will run whatever Tube services we can on those four days, based on the staff that sign into their shifts. All customers are advised to allow more time for their journeys.
"Extra bus and river services will run to help Londoners get around and roadworks will be suspended wherever possible. Additional Santander Cycles hubs will be in place at key central London locations to make cycling an easier option."
