Talks aimed at averting a Tube strike on the Piccadilly Line on Christmas Eve have ended without agreement.
Drivers belonging to union Aslef voted to walkout after a colleague's demotion for passing through four red signals.
They will also walkout for 24 hours on the line, which serves Heathrow, on 5 January as part of the dispute.
London Underground (LU) said some services would run on Friday even if the strike goes ahead but they hope talks will continue.
'Necessary tests'
Last Friday talks between LU and the Rail, Maritime and Transport (RMT) union also ended without resolution.
The union will ask members to vote this week on whether to take industrial action in a row over pay, hours and potential job cuts.
If the ballot of signal workers backs action, the walkout could take place on New Year's Eve.
An LU spokesman said strikes would not resolve the row over the Piccadilly Line driver.
He said: "He (the driver) has not been sacked, but downgraded for nine months, after which time he
can re-apply to be a driver provided he passes the necessary tests.
"We will continue to seek talks with Aslef to resolve these issues."