The distance or width between the inner edges of the heads of the rails; (1) in coal mining, the rail gage for tub and car tracks ranges from 2 to 3 ft (0.6 to 0.9 m), and 2-1/3 ft (0.7 m) is considered a satisfactory compromise; (2) the standard gage for railway tracks is 4 ft, 8-1/2 in (1.44 m) and, (3) in metal mining, the rail gage ranges from 1-1/2 to 2-1/2 ft (0.46 to 0.76 m).