Intermittent inductive automatic train stop

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For other uses, see
Automatic Train Stop
.

The intermittent inductive automatic train stop (also referred to as IIATS or just automatic train stop or ATS) is a

cab signaling and automatic train control
systems. The system remains in use after having been introduced in the 1920s.

Overview

F40PH

The technology works by having the state of a track mounted "shoe" read by a receiver mounted to a

failsafe
when the shoe is energized it presents an "off" state to the receiver, while the non-energized state presents an "on" state which triggers an action. This allows things like permanent speed restrictions or other hazards to be protected by non-active devices.

The receiver consists of a two coil electromagnet carefully aligned to pass about 1.5 inches above the surface of the inductor shoe. The inductor shoe consists of two metal plates set into a streamlined housing designed to deflect impacts of debris or misaligned receivers. The metal plates are connected through a

accidental activations
when the train passes over switches or other metal objects in the track area.

The most common use case for the ATS system was to alert the

railroad engineer of an impending hazard and if the alert was not acknowledged, stop the train by means of a full service application of the brakes. When attached to signals the shoe would be energized when the signal was displaying a "Clear" indication. Any other signal indication would de-energize the shoe and trigger an alarm in the cab. If the engineer did not cancel the alarm within 5–8 seconds a penalty brake application would be initiated and could not be reset until the train came to a complete stop.[1] Unlike mechanical train stops or other train stop systems, IIATS was not generally used to automatically stop a train if it passed a stop signal and in practice could not be used for this purpose as the shoes were placed only a few feet from the signal they protected and would not present sufficient braking distance
for the train to stop.

On bi-directionally signaled lines two "shoes" would be needed, one for each direction of travel as locomotives would only have a sensor to detect the shoes on one side of the train. The receivers can also be designed for easy removal to prevent damage when operating in non-equipped territory or to cut costs when only a small portion of the railroad requires ATS equipped locomotives. "Inert" inductors are sometimes placed in advance of certain speed restrictions as an alert or at engine terminals to test the functionality of the ATS system.

On a few

light rail vehicles can be brought to a stop much more quickly than a mainline railroad train without requiring complex signal overlaps

Use

RiverLINE to enforce absolute stops at interlockings
.

Starting in the 1930s the US

Chicago and North Western Railway
installed the system on some of its Chicago area commuter lines.

After the

Atchison, Topeka and Santa Fe choose to fully equip its Chicago to Los Angeles and Los Angeles to San Diego main lines in support of the Super Chief
and other premier high speed trains.

IIATS installations reached their peak in 1954 with a total of 8650 road miles, 14400 track miles, and 3850 locomotives equipped with the system. However, with the collapse of long distance passenger rail travel and the general North American railroad industry malaise in 1971, the bankrupt

Union Pacific on behalf of Metra

When the NJ Transit River Line opened in 2004 it featured a new IIATS system. This is a light rail systems running on shared track with main line freight traffic and IIATS is used to enforce a full stop at equipped signals instead of as a warning system.

See also

  • Indusi
  • Automatic warning system
  • Le Crocodile
  • Cab Signal System

References

  1. ^ a b c "A look at Automatic Train Stop (ATS) – RailPAC".
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