US signals

[Anonymous]

I am a user of the TRAINZ rail sim program but I can't get my head round how the signalling system worksin the USA. I live in the UK which has a different system.
Can any one explain the different types of signals in the US and where they would be placed on a layout.

[Anonymous]

This is an almost impossible answer, because North American signal practice varies wildly by railroad and over time. Here's a link that will take you to recent Union Pacific practice: http://www.lundsten.dk/us_signaling/aspects_up1988/

Note that signals have indications (what you see); names (what they're called), and indications (what you do when you see the indication).

The presence or lack of a number plate is significant; on many North American railroads the lack of a number plate indicates the signal is an Absolute, and that signal grants authority to occupy the track it protects. The presence of a number plate indicates the signal is an Automatic Block Signal, which does NOT grant authority and merely indicates the condition of the track beyond it.

Absolute Signals, in very general terms, surround and protect control points, interlockings, crossings at grade, crossovers, junction switches, etc. -- anyplace that a dispatcher will want to grant authority to a train or protect a main track. Automatic Block Signals are placed at appropriate braking distances (and where they're visible as possible) at intermediate points between Absolute Signals. Most, but not all, Absolute Signals are controlled signals, that is, a dispatcher or operator can request it give a proceed indication (stop is default).

But there are many non-controlled Absolute Signals, such as at crossings at grade with another railroad or drawbridges. These signals respond to track conditions. So why the difference? An Absolute Signal indicating stop cannot be passed without oral or written permission from a dispatcher or operator, whereas Automatic Block Signals are usually stop-and-proceed at restricted speed (half the limit of vision, and not more than 20 mph), and sometimes not even the stop is required. Obviously, you don't want a train doing a stop and proceed at a diamond or drawbridge, but you don't need a dispatcher or operator to control that signal in all cases, either.

This is incredibly brief. A broad, general, introductory explanation of common North American signal practice would take about 20,000 words and a lot of diagrams. Trains did a two-part article back in the 1950s that was very good; we're in the process of updating that article so we can run it again, because a lot has changed (and a lot hasn't).

[TH&B]

One of the simplest systems is to just set up ABS with single aspect signals. All they do is act like block signals with red, yellow and green. Place one for every block per direction, any swich (or points) you throw in the block or any train in the block turns the signal red. You can pretty much apply this to any layout as long as you don't have level crossing with another rail line, but it is easiet if your line is double track so each line is signaled one direction. All yard tracks and sidings are unsignaled. Some subdivions that's all there is (was). Trains magazine had a good article about the Santa Fe ABS within the last year or so.

[Anonymous]

Thanks Folks for the info. I am attempting to incorporate correct signaling into my Trainz rail sim layouts