From: frankk@cwi.nl (Frank Kuiper)
Newsgroups: rec.railroad
Subject: Re: flashing signals
Date: 18 Nov 92 11:00:49 GMT


   In <1992Nov18.030939.6935@mailhost.ocs.mq.edu.au>
   eoliver@laurel.ocs.mq.edu.au (Eddie Oliver) writes:

   However perhaps we can now get back to the original line of
   enquiry, which some of us (again myself included) have allowed to
   get lost. I was trying to find out - as were others later - a
   definitive statement of the systems adopted around the world. 

   What we haven't yet established is which railroad systems use
   which varieties.  We know that New South Wales is pulsating, and
   it was said that British Rail appeared to be pulsating but of
   type 2 above; can others advise their local situation, especially
   re different US and Canadian systems?

   Eddie Oliver

The Dutch railways (NS=Nederlandse Spoorwegen) use pulsating signals
(I would have called them flashing, if not for this discussion).
The main NS signals are quite simpel:
	red - stop
	yellow - slow down to low speed (40km/hr), expect to stop
	green - proceed

Some signals have additional speed indicators, which used with a
yellow light mean: slow down to given speed.  If the speed indicator
is out of order, the more restrictive 40km/hr is enforced.
A green light with a speed indication is also possible, but in this
case the green light is pulsating.  This mostly happens at junctions
along the line, where the turns have different allowed speeds,
depending on the direction, curves, etc.

Within a station area, so called "lower placed signals (aka "dwarf
signals") are used.  These are positioned most often at about a
hight of less than a yard above the top of the rail, next to the
track.  These signals are only passable at a maximum of 40km/hr,
even if green is displayed.  In these signals, a pulsating yellow
means "expect track to be occupied".  This happens very often, as
the NS use trains which can be coupled and uncoupled at stations;
two trains meet from two directions, join and continue in a third
direction.  There is also a meaning for pulsating green, but I can't
think of what it is, and I don't have my books at hand.

These pulsations have a frequency of approximately two per second.

A flashing red signal is used as a tail light for fraight trains.
It's a battery powered light, easily removable and fixed to any
fraight car.
Passenger trains (almost always) have two fixed red lights.

Other flashing lights are used at grade crossings, both white (no
train coming, system opperation) and red (train approaching); and to
indicate a train approaching at points where the track is obscured
by bridges, curves, etc.  These latter are white lights, placed
high, so as not to be obscured by a passing train on another track.
Steady white lights in this case means: track (section) clear.

I'll have to check my documentation to see if I missed anything.

-- 
Frank Kuiper                                       .                  ___   
Internet: frankk@cwi.nl                                          _][__| |
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