• Hypothetical speed signaling question

  • General discussion about railroad operations, related facilities, maps, and other resources.
General discussion about railroad operations, related facilities, maps, and other resources.

Moderator: Robert Paniagua

  by MattW
I've been becoming very acquainted with signals and the various dialects across the country, I'm particularly fond of NORAC and CSX speed signaling but a hypothetical situation has me puzzled. Here's the setup, a new commuter rail service is to begin operations and to keep traffic flowing, the agency has specified 80mph crossovers in 80mph (79) territory to thread passenger trains around freight trains without delay. Under NORAC or CSX, what would the setup likely be for the distant and home signals for a diverging movement over one of these high speed crossovers? I know the NEC uses flashing-green "cab speed" for this kind of thing, but what about a non-cab-signaled line? I could imagine some kind of odd hybrid route/speed signaling with maybe "approach diverging clear" followed by "diverging clear" allowing full-speed movement, but it still doesn't feel quite right.
  by ExCon90
As far as NORAC is concerned, there's nothing in the book that they could pull out and use. The PRR always had a section in its employee timetables headed "Signal aspects not in conformity with typical aspects, in service:", followed by an illustration of the non-typical aspect and a precise statement of where located and its meaning. Based on past practice, they might use directional arrows (used today at HAROLD and for the gauntlet track at New Carrollton, and for the gauntlet track in the B&P Tunnel in Baltimore, which I think I read is no longer in service). One way it could work is to display Clear on both the distant and the home, regardless of route, with a vertical arrow (on both the distant and the home) when the route is lined straight and a horizontal arrow when diverging. This should be legitimate if the turnout is good for 80mph, since without cab signals the maximum speed for either route would be 79mph and thus no speed reduction for the turnout would be necessary (which is the point of having an 80mph turnout in the first place). This would avoid tinkering with established typical aspects, which should be reserved for situations requiring a change in speed.