London Tube drivers on two lines are going on strike for 24 hours from 9:30pm tonight, forcing the closure of the Hammersmith & City and Circle lines.
Members of the Rail, Maritime and Transport (RMT) union are walking out after claiming industrial relations have broken down.
RMT has accused Transport for London (TfL) management of being "heavy handed" with drivers over issues such as timing staff toilet breaks with a stopwatch.
The union also claim TfL showed a "flagrant disregard" for agreed work policies and procedures.
RMT general secretary Mick Cash said: "This dispute is about the basic issues of protecting working conditions of our members and defending agreements from attempts to drive a coach and horses through them."
Transport for London said there will be no Hammersmith & City line service and a very limited service on the Circle line from around 9pm and all day Friday.
Steve White, operations director for London Underground, advised passengers to check travel information.
He said: "All other Tube lines and other TfL services will be operating as normal and we'll be making sure that everyone has the information they need to re-plan their journeys if necessary."
