How do elevators work?

In these traction elevators, the counterweight usually equals the weight of the car plus about 40 to 50 percent of its maximum load, so the motor only has to move the difference. Low buildings often use hydraulic elevators, which push the car up with a piston driven by oil under pressure. Safe passenger lifts became possible after Elisha Otis demonstrated his safety brake in New York in 1854, dramatically cutting the rope while standing on the platform. The first passenger elevator with his brake opened in a New York store in 1857. Modern elevators have several ropes, each strong enough to hold the car on its own, plus automatic brakes that grip the guide rails.