Axle track

Axle and wheel track are commonly measured in millimetres or inches.

[5] In the railroad industry, the term "axle track" is not used; the same concept is called "flange gauge" or "wheel gauge".

It is measured on a wheelset of a railroad car or tram from one wheel flange reference line to the reference line of the other wheel.

[6] The maximum and minimum limits to the differences between the two gauges are usually 111⁄32" and 3⁄8" (9–35 mm).

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Track (measured between center line of wheels)
The flange gauge – between the outer faces of a tram or railroad car's wheels on an axle (A) – is comparable to the axle track on other vehicles