>
> Bill,
>
> Thanks for explaining these aspects. One really needs to go through
> the aspects one by one in their logical order to understand their
> purpose. Now I gather that the signals are used in a comparable way
> as train orders: They show how to run and what other traffic to
> expect on the territory. So a lot more information needed to be
> conveyed to the crew.
>
> Actually I live in Germany. Most trains have fixed schedules.
> Switches are not operated by the crew except for switching
industrial
> spurs or some yard areas. So the crew needs only to know at what
> speed they had to go. No concern about priorities and such.
> Everything is done by the dispatcher.
>
> Different concepts in different worlds.
>
> Thanks for lighting up my perception.
>
> Manfred
> Bonn
Manfred,
Most of these signals that are, or were, in use are in CTC
territory. On the NYC a system similar to CTC was used where
operators controlled all switches at interlockings (little CTC
plants). In CTC the dispatcher does line all routes and the crew
only must know what speed it is expected to operate at while passing
a signal and approaching the next. Route at switches and crossovers
is mostly important only to the engineer to determine speed permited
on that route. Of course the simple signals of red, yellow and green
apply to ABS but not the "diverging" signals such as red over yellow
over red.
We don't need to know where the trains are but rather what the signal
will permit us to do. A red signal may mean a train is ahead but
often just means stop. (Dispatcher out having a smoke, trackmen
working, signal failure, broken rail etc.)
Some of the signals are needlessy complicated. For example BNSF uses
yellow over yellow, and flashing yellow to indicate approach medium.
But in reality flashing yellow is used in advance of a solid yellow
and yellow/yellow in advance of diverging. Also lunar and flashing
red mean proceed restricting but the lunar is used to enter non-
signalled track and the flasing red is used as a "drill signal" to
use a controlled switch for back and forth switching. So, the rules
don't tell you all the practices in a given area. Ya gotta know the
territory. I'm sure this applied to former CB&Q signals as well.
And finally signals, like all of us, are not perfect. I remember a
location where you could get a green, yellow, then 6100' later, a
red. This was 60 mph track and damn hard to stop a train in that
distance. I used full dynamic and full service to stop just at the
red signal. And this from seeing the yellow and beginning the
reduction well in advance (about 2000') of the yellow.
Another situation used a green-yellow-yellow-red sequence. (That's
green in advance of yellow in advance of yellow in advance of red.)
The double yellows were needed because the blocks were too short to
permit safe stopping with just one yellow. To make things worse the
red was the entrance to a 30 mph siding and you still got the two
yellows when lined into the siding. Many engineers were used to the
extra yellow and ran a little hot approaching the second yellow. One
day an engineer was running in usual manner when a train stopped at
the red decided to announce his location over the radio. The second
train, running hot, was expecting a second yellow and dumped the air
just in time to get stopped before plowing into the rear of the first
train. So, the complication of extra signal aspects is useful and
even with all the colored lights out there it is a tricky business.
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