In case you don’t know about Narrow Gauge, you should definitely ask … In the late 1800s, railroad gauge was standardized to 4 foot, 8 inches between rails. Some US railroads had a six foot gauge back then, and it made transfer from one railroad to the other a problem. But some railroads had another problem altogether: limited space for a right-of-way. These include logging, mining, and mountain railroads whose routes took them through tight curves, up narrow mountain ledges, and through difficult forests. The easiest way to deal with it was to have a narrower gauge track. A large part of the Denver and Rio Grande Railroad was narrow gauge, for instance, because of its routes through the Rocky Mountains and its mining operations. The distance between rails would be anywhere from two to three and a half feet.
In model railroading, there are folks who specialize in modeling these narrow gauge railroads. They denote their specialty by first giving the actual scale, and then the track width. Thus, HOn3 means HO scale (1/87) using a 3 foot gauge. By coincidence, HOn3 gauge is the same as the gauge of N track! And On30 (O gauge, narrow 30 inch gauge) is the same width as HO track. Thus some narrow gauge is like using larger trains on smaller track.