This is a copy of a posting that was just made in the steam & preservation forum. I’m also posting it here on the chance that someone who doesn’t regularly watch the steam forum may have information.
Here’s a question for the steam and/or signal techies that may be on this site.
On July 21, FRA published proposed rules on the installation of positive train control (PTC) on many main line routes, as required by recent Federal legislation. Briefly, the rule would require installation of PTC by 2015 on any Class I routes which (i) carry intercity or commuter passenger trains, or which (ii) carry 5,000,000 GTM and have any toxic by inhalation (TIH) traffic. FRA estimates that this will require PTC on about 69,000 route miles of main line track which, it says, comprise the “heart” or “core” of the Class I freight network. The rule will require the lead loco on any train operated on a PTC line to be PTC equipped (with some exceptions not here relevant). While the presence of excursion passenger trains on a line will not trigger a requirement to install PTC on that line, an excursion passenger train that operates on a line that is PTC equipped will have to be equipped.
Mainline steam excursions typically operate on major Class I mainlines, so it is likely they will be operating on lines which will be PTC equipped by 2015. That leads to my question. Is it even possible to equip a steam locomotive with PTC? Has anyone in the mainline steam camp looked at this issue? Inquiring minds want to know.
I’m sure the key word will be “waiver.” Aside from always putting a properly equipped locomotive behind every steamer, such movements will probably have to be specially handled - guaranteed clear blocks in both directions.
Of course, ATS, ATC, and Cab Signals were not connected to the throttle; the engineer had to act on what the signals told him. In a post on the Steam site, Crandell (Selector) describes what seems to be a workable link between the PTC and the steam throttle.
The question this raises is whether there’s any reason a PTC system needs to shut off the throttle on a steam loco. To my knowledge , the older ATC and ATS systems didn’t do so when the system imposed a penalty stop. While a diesel may shut down when the brakes are applied, I’m not sure why it’s necessary that a steam loco do so. There’s no way that the engine will be able to negate the brakes.
Sure. The US&S AR cab signal systems applied to PRR GP9s when new came out of PRR’s steam fleet. No need to close the throttle on steam for PTS, but you do have to be aware of what the full throttle, light engine, out of supplies, braking curve looks like. It’s going to vary from locomotive to locomotive based on tractive force from drivers versus braking force from all axles plus tender.