Jargoneer Wrote:
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> Hotwater, Thanks for your succinct response but
> for my simple-minded friend, who is highly
> literate by the way, could you explain in layman's
> terms why you answered "No" and "No"? We need a
> bone with some meat on it, if you know what I
> mean.

OK

1) ATC "Automatic Train Control" is a VERY old information in the rails system, that had only two aspects in the cab for the cab crew, A) green, or B) red for restricting. Once the alarm goes off and "restricting" is displayed, the Engineer MUST apply the automatic air brakes and quickly reduce train speed to below 20 MPH, all within a prescribed minimum time. If not, a penalty brake application is initiated. For example, the C&NW had this sort of ATC system, and it was always subject to inclement weather affecting the information in the track/rails. Once the UP merged with the C&NW, the UP then had to begin equipping most of their main line locomotives with the combined UP Cab Signal and C&NW ATC systems (including their 2 steam locomotives, 844 and 3985, and 4014 also is now equipped with both).

2) PTC is essentially a GPS based system with information transmitted continuously between the locomotive's on-board PTC computer system, and GPS satellite systems plus wayside ground units. Unlike the very old ATC system, PTC is constantly aware of train speed at any given location, Form B work zones and appropriate speed limits, other trains on the line, etc., etc., etc..