New York City is notorious for its subway system, connecting the entire city in an entirely different underground city. There is a lot of physics involved in the movement of the train cars, from beginning to end. The braking system of a subway involves the use of electromagnetic induction and Eddy currents. An electromagnet is attached to the train care and is positioned near the steel rail. Braking occurs when a large current is passed through the electromagnet. This relative motion of the electromagnet and the rails induces Eddy currents in the rails, creating a dragging force and slowing down the car. Because the Eddy currents steadily decrease in magnitude, this effect is seen as smooth to passengers.