Southern Rail plans to run six out of every 10 trains normally timetabled during the 48-hour strike by the Rail, Maritime and Transport (RMT) union that commences in the early hours of Wednesday morning.
The franchise said that it would use "contingency conductors", adding that there would be extra staff at stations to help passengers and "arrangements in place for passengers to use alternative transport providers".
"There will be a restricted service, with many routes having fewer trains, and, unfortunately, on some routes there will be no service at all," parent company Govia Thameslink said in a statement.
The industrial action is the latest in the long-running dispute between Southern Rail and the RMT over the role of guards on trains.
Despite overtures from both Southern and the RMT that they are ready to talk, no further talks are currently scheduled in advance of the strikes.
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