Track set at wrong gradient at 6,000 locations resulting in speed restrictions
Perished rubber pads between baseplates and track causes rails to become unstable at 17 locations (News last week) Train problems:
Automatic steering on curved track is faulty
Higher braking and accelerating loads wear track away more quickly. (News last week)
Many of the 12,000 signalling units date back to the 1960s and need replacing
If defects are detected during a night shift inspection Tube Lines has to decide whether it will be safer to impose a speed restriction or to carry out a repair which might run into operating hours.