P4 gauge
From open-encyclopedia.com - the free encyclopedia.
P4 gauge, also known as protofour, 4 mm finescale, and S4 is a model railway standard of 4 mm scale and accurate 18.83 mm gauge track. As the name implies, P4 gauge is accurately to scale for 4 mm scale modelling, while other track gauges (such as OO gauge and EM gauge) used for standard gauge prototypes are less accurate approximations.
As well as a track gauge, P4 also specifies the exact wheel profile and track parameters to use, which are largely an exactly to scale version of real life standards.
