brake, in technology: The Air Brake System

An early system for multiplying the braking force, called the air brake system, or air brake, was invented by American manufacturer George Westinghouse and was first used on passenger trains in 1868. It is now widely used on railroad trains. The fundamental principle involved is the use of compressed air acting through a piston in a cylinder to set block brakes on the wheels. The action is simultaneous on the wheels of all the cars in the train. The compressed air is carried through a strong hose from car to car with couplings between cars; its release to all the separate block brake units, at the same time, is controlled by the engineer. An automatic feature provides for the setting of all the block brakes in the event of damage to the brake hose, leakage, or damage to individual brake units. Railroad braking can be enhanced by collision avoidance systems that will stop train movement without human intervention in certain situations, such as when there is a danger of collision. In the United States, positive train control, a system that uses GPS devices, radio, and computers to automate emergency braking, was fully installed on some 58,000 mi (93,000 km) of track in 2020; it was first mandated by Congress in 2008. The air brake is used also on subway trains, trolley cars, buses, and trucks.

Sections in this article:

• Introduction
• The Vacuum Brake System
• The Hydraulic Brake System
• The Air Brake System
• Braking Systems
• Electric Brakes
• Friction Brakes

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