MODERN RAILROAD TRACK consists of two parallel steel rails clipped on to a support called a railroad tie. Railroad ties are usually made of reinforced concrete, although wood and steel are still used. The distance between the inside edges of the rails is the track gauge. It evolved in Britain, which uses a gauge of 4 ft 8½ in (1,435 mm), known as the standard gauge. As engineering grew more sophisticated, narrower gauges were adopted because they cost less to build. The loading gauge, which is equally important, determines the size of the largest loaded vehicle that may pass through tunnels and under bridges with adequate clearance. Safe train operation relies on following a signaling system. At first, signaling was based on a simple time interval between trains, but it now depends on maintaining a safe distance between successive trains traveling in the same direction. Most modern signals are color lights, but older mechanical semaphore signals are still used. On the latest high-speed lines, train drivers receive control instructions by electronic means. Signaling depends on reliable control of the train by effective braking. For fast, modern trains, which have considerable momentum, it is essential that each vehicle in the train can be braked by the driver or by a train control system, such as Automatic Train Protection (ATP). Braking is achieved by the brake shoe acting on the wheel rim (rim brakes), by disc brakes, or, increasingly, by electrical braking.
Train equipment
in
RAIL AND ROAD
published on 8:32 AM
MODERN RAILROAD TRACK consists of two parallel steel rails clipped on to a support called a railroad tie. Railroad ties are usually made of reinforced concrete, although wood and steel are still used. The distance between the inside edges of the rails is the track gauge. It evolved in Britain, which uses a gauge of 4 ft 8½ in (1,435 mm), known as the standard gauge. As engineering grew more sophisticated, narrower gauges were adopted because they cost less to build. The loading gauge, which is equally important, determines the size of the largest loaded vehicle that may pass through tunnels and under bridges with adequate clearance. Safe train operation relies on following a signaling system. At first, signaling was based on a simple time interval between trains, but it now depends on maintaining a safe distance between successive trains traveling in the same direction. Most modern signals are color lights, but older mechanical semaphore signals are still used. On the latest high-speed lines, train drivers receive control instructions by electronic means. Signaling depends on reliable control of the train by effective braking. For fast, modern trains, which have considerable momentum, it is essential that each vehicle in the train can be braked by the driver or by a train control system, such as Automatic Train Protection (ATP). Braking is achieved by the brake shoe acting on the wheel rim (rim brakes), by disc brakes, or, increasingly, by electrical braking.
