Night Tube service to begin on Piccadilly Line
The Piccadilly Line will become the latest route to begin a Night Tube service later.
It follows the launch of 24-hour services on the Central, Victoria, Jubilee and Northern lines.
The RMT union has called for the launch to be delayed due to "on-going safety concerns" connected to wet leaves damaging train wheels.
Transport for London (TfL) has insisted "there are no safety concerns" and the launch will go ahead as planned.
Commuters have faced disruption on the Piccadilly Line since last month when half its trains were taken out of service after the wheels were damaged.
Mick Cash, RMT General Secretary, said: "The fleet consists of 43-year-old trains that have recently had their wheels replaced, leading to serious problems.
"It is utter madness that while the service on the Piccadilly Line is at breaking point the company plan to run trains right through from 0500 [GMT] Friday morning until 0030 [GMT] Sunday."
A spokesperson for TfL said: "There aren't any safety issues. If there were we wouldn't be launching".
TfL added that despite having only 80% of operational trains running during its daytime Piccadilly service, it did have the necessary 25 trains needed to run the reduced night schedule.
The latest Night Tube service will run every 10 minutes between Cockfosters and Heathrow Terminal 5, barring Terminal 4, on Fridays and Saturdays.