Talks aimed at resolving the Southern Railway dispute have ended without agreement, the company said.
On Wednesday the train drivers' union Aslef said that "progress had been made" in talks but that Friday's strike would still go ahead.
It will be the third day of strike action this week, after members walked out on Tuesday and Wednesday.
Aslef is opposed to driver-only trains, citing safety concerns as passenger numbers grow, and warning that in-cab monitors, allowing them to check when it is safe to close doors, do not always work.
Nick Brown, chief operating officer of Southern's owners Govia Thameslink Railway, said: "We're deeply disappointed, as our passengers will be, that Aslef has been unable to accept our proposals and we cannot find a way forward to end this dispute with the drivers' union at this stage.
"We're sincerely sorry that commuters' work and family lives are being punished with this unjustified and unprecedented industrial action."
Southern Railway services will be at a standstill again on Friday after talks over driver-only trains collapsed.
Talks aimed at resolving the Southern Railway drivers' dispute will be held at the conciliation service Acas.
Commuters have been taking to social media to express their frustration at the latest Southern Rail strike.