Rail disruptions have hit London Overground commuters this morning.
Severe delays are affecting routes between Clapham Junction and Stratford and Richmond and Stratford.
Transport for London (TfL) said tickets will be accepted on the Tube and bus services, though a good service is present on all other routes.
The Piccadilly Line is running with minor delays eastbound between Northfields and Cockfosters this morning due to a signal failure.
The line is set for more strikes in November after RMT union drivers held industrial action in late September.
The strike will affect commuters on 7 and 8 November as drivers strike over an alleged bullying management culture.
RMT general secretary Mick Cash said: “RMT is frustrated with the slow and tortuous process when it comes to getting the Piccadilly Line management to address the full raft of issues at the heart of this dispute. That has left us with no option but to confirm this next phase of action early in November.”
Nick Dent, director of line operations for London Underground, said: “We met with the RMT at ACAS last week and continue to be available to meet with them in order to find a resolution for the dispute on the Piccadilly Line. We are disappointed that the RMT leadership have taken the decision to name new strike dates during these constructive discussions, and urge them to continue to work with us to resolve this dispute and spare our customers further disruption.”