The Secret Grip Of Cable Cars
Cable cars do not pull themselves along tracks. Instead, they constantly grip a hidden, fast-moving cable buried beneath the street and release their hold whenever they need to stop.
Unlike funiculars where cars are bolted to a rope, cable cars function like a street-level ski lift. A conductor manually operates a grip mechanism to latch onto the moving wire to accelerate or let go to brake. This clever system allowed steep city streets to be traversed by public transit long before electric engines became reliable. Today, only a few cities still use this mechanical marvel to climb their famous hills.
Source: Cable car (railway)