O scale refers to a model railroad train that is 1/48th the size of a real train—in the U.K., O scale trains are generally 1/43rd the size of the real thing while in Europe they are 1/45th as big. Like a real train, O scale model railroad trains run on two-rail tracks. The gauge of those tracks is O, which describes tracks whose rails are 1 ¼ inches apart. Even though O scale model trains frequently run on O gauge tracks, strictly speaking, the two Os have nothing to do with each other.

The letter "O" is actually a misnomer since the designation was initially conceived to identify trains that were smaller in scale than 1, which had been the standard. Since the only number smaller than 1 is 0, that’s how early O scale trains and O gauge tracks were identified. Similarly, HO was originally intended to describe a scale and gauge that is half (H) of zero, but the letter O (pronounced “owe”) crept into everyday use among model train buffs and has remained the way to refer to zero ever since.

Confused? A lot of people are. But for those who are first and foremost focused on O scale, nothing else matters. For these enthusiasts, replicating the detail of a full-scale train in an equally detailed layout is the only goal.

An O scale model train’s tracks, as it turns out, are a key part of creating a sense of realism. When an O scale train is run on three-rail O gauge tracks (the middle rail delivers the power to the locomotive) such as those made by Lionel, the train rides higher off the surface than it would in real life, thus shattering the illusion. Model railroaders who run O scale trains on three-rail tracks are known as hi-railers. It’s not quite a put down, but it isn't really a compliment, either.

Toy manufacturers in the early part of the 20th century originally embraced the O scale so they could offer customers model trains that took up less space than their standard-sized counterparts. Because they were smaller, these trains were also less expensive. At one time or another, Märklin, Lionel, MTH, Williams, Atlas, and Weaver, among others, all offered O scale trains. Fans of brass model trains are also frequently O scale acolytes because the earliest, most collectible brass trains made in postwar Japan were usually O scale.

The smaller scale took off in the 1930s, when affordability trumped most other concerns thanks to the Depression. The scale also benefited from its adoption by industry leader Lionel, which sold two O gauges for its O scale trains. Lionel’s regular O gauge track was the same width as its O-27 gauge track (1 ¼ inch), but the O-27 had a lower profile than regular O, and its thinner rails allowed all but the longest O scale model trains to make tighter turns (a circle of O-27 tracks has a diameter of 27 inches instead of 31).

Today, neither appeal to O scale purists who put accuracy and authenticity above mere convenience. There is even a vocal contingent of two-rail O scale enthusiasts who advocate for the conversion of model trains designed to run on three-rail tracks to model trains that will run on just two. This often requires changing a train’s trucks (the framework for the axles and wheels) as well as a layout’s wiring (from AC to DC), but the lower profile that results makes an O scale model train look a lot less like a toy and more like the real thing.

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Recent News: O Scale Model Trains

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Memphis Railroad And Trolley Museum Hosts Central Station's 100th ...
The Chattanoogan, September 14th

Ongoing exhibits in the museum that are favorites for youngsters include Thomas & Friends, the 1/8" scale live steam model engine of the Illinois Central Hudson locomotive #2499, the On30 model train layout modeling "O" scale using "HO" track and the ...Read more

Train Days returns to Los Altos: Museum highlights model railroading
Los Altos Town Crier, August 27th

Participants include the Live Steamers from the Bay Area Garden Railway Society (G scale); the Diablo Pacific Short Line (G scale); the Golden Gate Lionel Railroad Club (O scale); a private collector's Swiss Narrow Gauge (HO scale); Peninsula NTrak and ...Read more

Train club to hold Wm. Crooks Day event Aug. 30th
Northland Press, August 25th

On Saturday, August 30th, 2014 the Northern Minnesota Railroad Heritage Association (NMRHA) in Crosslake is holding a Wm Crooks Day History Event to educate the public on the history of the Wm Crooks Locomotive. The half-size scale model of the Wm...Read more

Photos: Railroad Museum hosts festival in Riverhead
Riverhead News Review, August 24th

The Railroad Museum of Long Island is hosting a festival this weekend to celebrate the 50th anniversary of the LIRR G-16 Park Train, which ran at the 1964 World's Fair in Queens. The festival ... Detail of Peter Miller's O Scale display. (Credit...Read more

Model train exhibit and free workshop at Mesa Library
East Valley Tribune, August 12th

Train enthusiasts will experience more than 300 feet of G-scale tracks with double main lines, garden size trains (1.5 to 2 times the size of O-scale Lionel trains), and dioramas with scenes from Arizona rail towns. ABTO members will be on hand to...Read more