Commuters are being warned to expect "severe disruption" on south London's tram network from Tuesday, due to the first of two two-day drivers' strikes.
Members of the Aslef union are planning industrial action in a pay dispute.
The first strike, on 28 and 29 June, is set to affect services from Wimbledon to Beckenham Junction and Elmers End, Transport for London (TfL) said.
TfL said extra buses would be running in areas along the route, but they were expected to be busier than usual.
Customers have been advised to check the latest information before they travel, allow more time for their journeys and seek alternative routes, such as walking or cycling.
The action is set to be followed by another two-day strike on 13 and 14 July, Aslef said.
The union said its members had been offered a 3% pay increase, which it said was a real-terms wage cut, and it wants to see a pay rise in line with inflation.
Finn Brennan, who represents tram drivers said: "Our members do a difficult and demanding job, working round the clock shifts over 364 days of the year. They deserve a fair pay settlement."
Trish Ashton, TfL Director of Rail and Sponsored Services, said: "We are disappointed that Aslef have decided to take industrial action on the tram network and urge them to meet with Tram Operations Ltd, the operator, to try and resolve this matter and avoid disruption to our customers."