Trackside Signals


Strictly speaking, the visual signals alongside the track on a model railroad are not required for operation, because there are no drivers inside the trains who need to see the signals and act upon them.  However such signals make a model railroad more visually interesting.  After all, who doesn’t like a few colorful blinking lights?

The primary purpose of most signals is to indicate whether or not a train is permitted to proceed past the signal, and often if a speed restriction is in place.  Multiple-head signals can also indicate whether a turnout following a signal is set to direct the train down a main route or a siding.  The signals I will be prototyping are not very complex, but I’m especially interested in mimicking some cool visual effects.

The YouTube video below shows examples of both types of signals I describe on this page: the color-light signal (green), and the obstruction-warning signal (rotating red).

Color-light signals

The most common type of signal is a multi-color signal with at least two distinct aspects or combinations of lights and colors.  They can get very complex, even in Japan (see Wikipedia article here).  For this testbed layout, I will be controlling simple two-aspect (green over red) starting signals for trams departing the platforms, like the one in the video below, taken from Iwasehama Station, the north terminus of the Toyama Light Rail.

Thankfully I don’t have to manufacture the signals themselves; there are a few companies which already make the signals in N scale (1:160) using very small LEDs.  They’re actually a bit small compared to the N-gauge PORTRAMs (1:150 scale), but that’s better because the signals used by the Toyama Light Rail system are a little smaller than those on regular rail lines.

Obstruction-warning signals

One type of trackside signal which I think is unique to Japan is the obstruction-warning signal.  Two designs are in use, the “corncob” or vertical group of rapidly flashing lights, and the “kuru kuru paa” pentagonal signal head with lights illuminating in a rotating pattern.  It’s the pentagonal signal which I want to include in my layouts.

As far as I could tell while visiting Toyama in 2015, the Toyama Light Rail system doesn’t employ obstruction-warning signals, probably because the trams have a short braking distance compared to regular trains.  But I’m planning to incorporate these signals into my larger layout eventually, so I’m including them in this testbed project.

Like the two-aspect signals mentioned in the previous section, I don’t have to scratch-build the signal heads and posts; a Japanese manufacturer makes N-scale plastic models of the signals, and I already have a package of those signals.  Unfortunately, they’re not equipped with LEDs, so I’ll be modifying them using (probably) surface-mount red LEDs and short lengths of optical fiber so the signals can be illuminated in a realistic manner.  I’ll be using a Texas Instruments MSP430-class microcontroller chip to drive the LEDs in sequence.