Prototype Gauge 4'8 1/2" = 1.177083333

NMRA Standard Gauge is min 1.25" to max 1.285" (S-1.2 Standards for Scale Models)

On30 uses HO scale wheel and track geometries, as specified in S-3.2 and S-4.2.

Rail Sizes

Rail Size	Scale Size	Proto Size
Code 55	2.64"	20 lb
Code 70	3.36"	35 lb
Code 83	3.98"	55 lb
Code 100	4.8"	75 lb
Code 125	6.0"	100 lb / 110 lb
Code 148	7.1"	130 lb

O Scale Track Dimensions
O Scale Ma and Pa Flat Car Drawings
O Scale Plymouth 20 Ton Locomotive

References

New Haven 1937 AAR Box Car
The O Scale Resource Magazine
Colorado O Scale Modelers
O Scale Trains Magazine
Proto 48

Products

Atlas O Scale Trucks and Couplers
Athearn O Scale Archbar trucks (discontinued)
Athearn O Scale Andrews trucks (discontinued)
Athearn O Scale Bettendorf trucks (discontinued)
Kadee O Scale trucks
Right-o-way rail, spikes
Midland Products Cork Roadbed 3' (25 pieces)
Woodland Scenics O Scale Products
Woodland Scenics O Scale "Trackbed"
Code 125 rail
Kadee O Scale wheels and trucks
Wiseman Model Services Trucks and other parts
All Nation Line
American Scale Models O Scale
La Belle Woodworking