Intermittent inductive automatic train stop

The inductor shoe consists of two metal plates set into a streamlined housing designed to deflect impacts of debris or misaligned receivers.

When the circuit is closed the choke eliminates the magnetic field and the voltage induced by it allowing the locomotive to pass without activation.

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.

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.

Those railroads still interested in high speed operations IIATS met the minimum ICC requirements with a lower cost compared to other cab signaling or automatic train control systems, however with rail travel facing increased competition from cars and airplanes most railroads simply choose to accept the new speed limit.

However, with the collapse of long distance passenger rail travel and the general North American railroad industry malaise in 1971, the bankrupt Penn Central was permitted to remove IIATS from its Water Level Route along with the Southern and other railroads with test or pilot IIATS systems.

Even the ATSF and successor BNSF were gradually allowed by regulators to remove IIATS from parts of previously equipped lines due to the reduced passenger traffic.