London Underground and the mechanisms are regularly degreased to lower the potential for fires. The only wooden escalator not to be replaced was at Greenford station, which remained until October 2015 when TfL replaced it with the first incline lift on the UK transport network. There are 426 escalators on the London Underground system and the longest, at , is at Angel. The shortest, at Stratford, gives a vertical rise of . There are 184 lifts, and numbers have increased in recent years because of investment making tube stations accessible. Over 28 stations will have lifts installed over the next 10 years,
North End tube station on 22 June 1907, running through the abandoned station. The uncompleted platforms and lower passageways remain, with access to the tracks. During World War II these were used to store secret archives with access only available from the cabs of passing service trains. During the Cold War a shaft was dug down to the lower passageways and the abandoned station became part of the London Underground's civil defence preparations. As the tunnels were the deepest in the network it was an ideal site. The role of the control centre was to manage the emergency floodgates placed throughout the tube network