# IIATS vs PTC



## seat38a (Oct 13, 2016)

Right now, the Pacific Surfliner and Southwest Chief can travel at 90mph since ATSF equipped their tracks with IIATS. Will IIATS equipped tracks still need to add PTC or are those tracks exempt? IIATS pretty much does the same thing as PTC?


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## jis (Oct 13, 2016)

No IIATS does not meet the PTC requirements. For one thing IIATS does nothing about speed limit enforcement. It also does not guarantee stopping short of fouling point at control points. Those tracks have to and are getting PTC. Even the NEC cab signal had to be augmented to meet the requirements of PTC.


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## seat38a (Oct 13, 2016)

jis said:


> No IIATS does not meet the PTC requirements. For one thing IIATS does nothing about speed limit enforcement. It also does not guarantee stopping short of fouling point at control points. Those tracks have to and are getting PTC. Even the NEC cab signal had to be augmented to meet the requirements of PTC.


Will the trains still be able to continue the 90MPH or faster?


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## jis (Oct 13, 2016)

That depends on how BNSF chooses to set up the system and maintain tracks. There should be no technical hindrance in maintaining 90mph or even going up to 110mph. Beyond that becomes a much more expensive proposition.


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## seat38a (Oct 13, 2016)

jis said:


> That depends on how BNSF chooses to set up the system and maintain tracks. There should be no technical hindrance in maintaining 90mph or even going up to 110mph. Beyond that becomes a much more expensive proposition.


So as long as track conditions allow, PTC can allow 80mph+ without in cab signaling?


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## jis (Oct 13, 2016)

The PTC system has to be set up to handle specific allowed speeds. It is not just track condition. There is a whole host of other things that need to be set up. PTC is cab signaling or its equivalent with more stringent enforcement than cab signaling. For example cab signals can only enforce signal speeds and typically cannot enforce safe absolute stops. PTC is required to enforce all civil speed restrictions, not just signal speeds. It is also required to enforce safe stop short of signals at danger at control points.


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## seat38a (Oct 14, 2016)

jis said:


> The PTC system has to be set up to handle specific allowed speeds. It is not just track condition. There is a whole host of other things that need to be set up. PTC is cab signaling or its equivalent with more stringent enforcement than cab signaling. For example cab signals can only enforce signal speeds and typically cannot enforce safe absolute stops. PTC is required to enforce all civil speed restrictions, not just signal speeds. It is also required to enforce safe stop short of signals at danger at control points.


Thanks! Great info. So effectively, the original reason for the 79mph limit will be gone once PTC is fully rolled out.


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## jis (Oct 14, 2016)

As long as the PTC system is deployed for speeds higher than 79mph.


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