Andy Sperandeo <asperandeo@...>
In the first place, I think your questions are off-topic for this list, and there's another
Yahoo list, the Ry-ops-industrialSIG list, that deals directly with these matters. But here
are some brief answers:
First, the movement of freight trains has often been anything but rigidly scheduled. In the
period covered by this list many railroads operated freight trains as extras without any
timetable authority, and that's the prevailing mode in today's railroading although the
term "extra train" is no longer used. Railroads that did use second-and third-class
schedules for freight trains often used them as schedules of convenience, meaning that
any train prepared to move within the span of a given timetable schedule might use the
train number of that schedule. Second- and third-class schedules generally functioned as
moving windows of authority with a 12-hour span (because unfulfilled timetable
schedules expire after 12 hours). So that part of your premise was incorrect.
Train order signals are used in a timetable-and-train-order operating regime to indicate
whether clearances and orders are to be delivered to passing trains at a station or train
order office. (They typically aren't used at subdivision or district terminals, since all trains
require at least a clearance card at their initial station.) When three-indication signals are
used, a green or vertical aspect indicates no orders, a yellow or 45-degree aspect
indicates orders to be delivered as the train passes, or "on the fly," and a red or horizontal
aspect indicates orders requiring the conductors' or trainman's signature, meaning the
train must stop.
As to why they are so seldom modeled, most model railroads don't operate in very close
adherence to prototype rules. Those that do and that use timetable-and-train-order
movement authority usually have train-order signals of some type. Typically train order
signals are not used with Centralized Traffic Control.
In HO scale, operating train order signals are available from Tomar Industries. See the
manufacturer's listings on the NMRA Web site at www.nmra.org.
My apologies for this divergence from freight car topics.