🚀 go-pugleaf

In article <BzGzsI.1u4@chinet.chi.il.us>, drx@chinet.chi.il.us (Scott Whittle) writes:
 > Ok I'll bite.  How does the railroad control the crossing gates?  Here in
 > Illinois, Chicago and NorthWestern changed over the technology at the
 > crossings about 2 years ago and have had major problems ever since.  Gates
 > come down and stay down without a coming locomotive.  Once I watch the gates
 > come down when the train (albeit moving about 3mpg) was about 25 feet from the
 > intersection.  
 > 
 > I've also noticed that commuter trains will cause the about 5 gates to come
 > down ahead, but a freighter will only bring down 3 ahead.  Anybody will
 > any knowledge they would like to share???


A dozen years ago I worked for a Kansas City based firm that sold railroad
trafic control systems.  In a nutshell, the way the systems worked then was
that a train would cause a short as it rolled over certain pieces of track.
This would cause the gates to drop.  (In the field behind our plant there
was a crossing gate going through a "life time" test.  Twenty four hours
a day it would go up and down, up and down, up and down.  They had a twelve
foot fence topped with barbed wire because the local kids used to grab on
and ride the gate.)

The dispatchers would sit and watch a light board that showed where each train
was and the status of each switch.  It took quite a few seconds to send a
signal to throw a switch before it propagated through the antique relays
in the field, performed the action, and returned a signal.  It was real-time
processing where events could take minutes to transpire.

Of course, all this was running on a PDP-11/34.  Ah, the good old days!

					Andrew MacRae
					
ps: Do you know what is different about the Chicago Northwestern line than
    all the other major railroad lines in the US?