Of Gauge and Scale

There was a recent question on the TY Facebook page asking about what railway track to use for terrain, and the discussion that followed has driven me to write this post on the topic.

The first key concept for railway miniatures is scale ratio, which relates to the size of the rolling stock relative to the full sized original.

The other concept is track gauge, which is the distance between the inner edges of the rails. Half of the world's railways, including those in France, Germany and Poland, have a gauge of 1435mm, which is known as Standard Gauge.

All model railway track, rolling stock and accessories are sold at a particular scale, which in this context refers to a specific combination of scale ratio, track gauge, and other factors that makes up the parameters of the system as a whole.

Scale	Scale Ratio	Track Gauge	Scale Error for Standard Gauge
O	1/46	32mm	+6.4mm at 1/56
S	1/64	22.5mm	-3.1mm at 1/56
OO	1/76	16.5mm	+2.2mm at 1/100
HO	1/87	16.5mm	+2.2mm at 1/100
TT	1/120	12mm	-2.4mm at 1/100
N	1/160	9mm	-5.4mm at 1/100
Z	1/220	6.5mm	+1.7mm at 1/300

For most scales, the scale ratio and the track gauge combine to create an accurate representation of a Standard Gauge railway. OO is a bit of an oddball where the track is underscale compared to the rolling stock for historical reasons. There are a multitude of other specialty scales, usually for narrow gauge prototypes. An example is NZ120, which is 1/120 on 9mm track, to represent New Zealand's railway network which has a gauge of 1067mm.

Obviously none of these are a perfect match for representing Standard Gauge in common wargaming scales. In 15mm you would require rolling stock with a scale ratio of 1/100 running on a track gauge of about 14.3mm, so it comes down to what compromises you are prepared to make: do you accept something too large, too small, do you go and scratchbuild your own, or do you simply avoid the problem?

I don't know why Battlefront chose to base their 'Battlefield In A Box' railway track on TT, but it seems to have led to an apparently widely-held but incorrect idea that TT is the perfect match for FOW. In reality, neither the track nor the rolling stock are any more accurate in 15mm than HO. As noted before, not all railways have the same gauge: in Russia the gauge is 1520mm, so for Eastern Front terrain the TT track is even more underscale than it is for the vast majority of rail lines in Northwest Europe.

From my perspective, what would be ideal would be a range of 1/100 rolling stock and accompanying 14.3mm track to use for 15mm wargames, with the next best thing being 1/100 rolling stock that sits on HO track, but alas as far as I can tell there is no such thing on the market. As such, wanting to have railway lines in my collection of TY terrain but being too lazy to scratchbuild, I have chosen to run with HO because of its price and availability, and am happy to accept that everything will be slightly too large.