Transport for London recently revealed the interesting above video and other details on how it maintains, replaces and continually upgrades its vertical-transportation equipment. The London Underground’s care of its massive collection of 440 escalators and 184 elevators involves a smart strategy of inspections and timetables. The hardworking escalators are checked and maintained every week, refurbished every 20 years and replaced every 40 years (except, apparently, the ones in the video that have been there 80 years). “Physical and geological considerations mean that every escalator on the London Underground network is custom-built for its location. Many components are made bespoke by the manufacturers, which mean a stockpile of spare parts can’t be built up,” London Underground Capital Programmes Director David Waboso commented, though the increasing modularity of newer units helps when something goes wrong.