Automatic Train Control

Automatic train control (ATC) is a general class of train protection systems for railways that involves a speed control mechanism in response to external inputs. ATC systems tend to integrate various cab signalling technologies and they use more granular deceleration patterns in lieu of the rigid stops encountered with the older automatic train stop technology. ATC can also be used with automatic train operation (ATO) and is usually considered to be the safety-critical part of the system.

Over time there have been many different safety systems labeled as "automatic train control". The first was used from 1906 by the Great Western Railway, although it would now be referred to as an AWS (automatic warning system). The term is especially common in Japan, where ATC is used on all Shinkansen (bullet train) lines and on some conventional rail lines as a replacement for ATS.

The accident report for the 2006 Qalyoub accident mentions an ATC system.

ATC-1 is used on the Tōkaidō and Sanyō Shinkansen since 1964. The system used on the Tōkaido Shinkansen is classified as ATC-1A and ATC-1B on the Sanyō Shinkansen. Originally utilizing trackside speed limits of 0, 30, 70, 110, 160 and 210 km/h, it was upgraded to utilize speed limits of 0, 30, 70, 120, 170, 220, 230, 255, 270, 275, 285 and 300 km/h with the introduction of new rolling stock on both lines. Variants include ATC-1D and ATC-1W, the latter being used exclusively on the Sanyō Shinkansen. Since 2006, the Tōkaidō Shinkansen's ATC-1A system has been superseded by ATC-NS.

Used on the Tōhoku, Jōetsu and Nagano Shinkansen routes, it utilized 0, 30, 70, 110, 160, 210 and 240 km/h trackside speed limits. In recent years, ATC-2 has been superseded by DS-ATC.

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