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An O scale glossary of sorts

I just spent some time explaining some of the terminology that goes along with Lionel and other O gauge and O scale trains. That made me think maybe a definition of some terms might prove useful to somebody. So here’s an O scale glossary.


Gauge is the width of the track. O gauge track is 1.75 inches wide. “Gauge” and “Scale” are often used interchangeably but they aren’t the same. Very few Lionel trains made up until the mid-1990s that ran on O gauge track were actually true O scale.


Hi-rail is realistic scenery using toy trains. The term originated because Lionel O gauge and American Flyer S gauge track are much taller than scale.

Narrow gauge

Narrow gauge is track that is less than 4’8.5″. This was used for short, private railroads (such as in and around mines) and in mountains, where smaller trains presented a cost or mechanical advantage. Some modelers model narrow gauge lines because it can be possible to model an entire railroad in a relatively small space. Narrow gauge models are designated as the scale, followed by the letter n, and the track gauge, i.e. HOn2, On30.


O27 is the cheapest track system used by Lionel, Marx, Ives, and American Flyer. A circle of O27 track measures about 27 inches from one side to the other. This curve is very sharp, so trains intended to run on O27 track tend to be undersize.

O27 profile

O27 track stands about 3/8 of an inch high, so “O27 profile” track refers to straight and wide curves that will plug into O27 track.


O31 was Lionel’s costlier, more durable track. Its wider curves allowed for bigger trains, and since the rails were made of heavier metal, sometimes it can withstand being stepped on. A circle of standard O31 track measures about 31 inches in diameter.

O31 profile

O31 profile track is straight sections and wide curves made the same height and thickness as O31 curves.


On30 is narrow gauge trains running on track that’s a scale 30 inches in gauge. This was popularized by Bachmann, because HO scale track is very close to 30 inches wide in O scale. Bachmann seized this idea, using HO track and mechanisms to make O scale trains. There wasn’t a lot of 30-inch gauge track in the real world, but it caught on and now is possibly the largest-growing segment of the hobby.


Prewar refers to trains made before World War II. By and large these trains are more colorful and less realistic than those made after World War II.


Postwar refers to trains made after the end of World War II but before Lionel Corporation sold its train line to General Mills in 1969 and turned itself into a toy store chain. Technology advanced rapidly during these years, allowing the trains to become more realistic and gain new features. Since these are the trains Baby Boomers grew up with, they are very popular.


Scale is the size of a model in relation to the real thing. O scale is 1:48, meaning a quarter inch on the model equals a foot on the real thing. S scale is 1:64, meaning 3/16 inch on the model equals a foot on the real thing. An O scale model of a 6-foot tall human being is 1.5 inches tall. When people talk about “scale trains” in the context of O gauge, they generally mean 1:48 scale trains of recent production that have much greater detail and scale fidelity than trains produced during the postwar era.


Semi-scale is a non-phrase that caught on within the O scale community. It refers to items that are something other than 1:48 scale. They’re still scale items, but not exactly the scale they are looking for. Holiday villages are a good example.

O scale hobbyists often settle for slightly off-scale items due to scarcity of accurate 1:48 scale models of things they need, such as vehicles. 1:48 vehicles are hard to find.

Standard Gauge

Standard Gauge (capitalized, as in proper noun) refers to large-scale Lionel trains made until the 1930s. There was actually nothing standard about it, but it caught on. They were big, loud, gaudy, colorful, and toylike.

standard gauge

Standard gauge (lowercase) refers to four feet, eight and a half inches. This is the standard width of railroad track. When someone talks about “standard gauge O” or “standard gauge HO,” they’re talking about an O scale model of a standard gauge train.

Super O

Super O was a form of track introduced by Lionel in the late 1950s to address some of the shortcomings of tubular track. It was much more realistic, and while it developed a cult following that remains to this day, it didn’t really catch on.


Before plastics, most trains were made of tin-plated steel that was formed into shape. Either the metal was printed with a design (usually lithography) before it was formed, or it was formed and then painted with enamel paints.

Tubular track

Tubular track is the oldest form of toy train track, invented by Marklin in the 1890s, made of steel sheet formed into a tube and crimped onto a small number of large, oversized ties. Lionel’s O27 and O31 track are both tubular. A number of companies now offer newer track with a higher degree of realism.

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