On30

On30 uses the 1/4" to the foot, (ratio 1:48) to operate trains on HO gauge (16.5 mm gauge) track. The 30 indicates the scale/gauge combination is used to model 2 ft 6 in (762 mm) (30") narrow gauge prototypes, although it is often used to model 2' and 3' gauge prototypes as well.  On30 is regarded as the fastest growing gauge/scale combination. Proponents of the scale suggest the appeal lies in the models representing "quaint" narrow gauge prototypes. The scale gives the models a certain bulk, and allows details to be easily seen. At the same time electrically and mechanically it is the same as the very popular HO scale, ensuring reliability of operation.

For more, visit the On30 Forum.