49 CFR 213.355 - Frog guard rails and guard faces; gage.
The guard check and guard face gages in frogs shall be within the limits prescribed in the following table -
|Class of track||Guard check gage||Guard face gage|
|The distance between the gage line of a frog to the guard line 1 of its guard rail or guarding face, measured across the track at right angles to the gage line, 2 may not be less than -||The distance between guard lines, 1 measured across the track at right angles to the gage line, 2 may not be more than -|
|Class 6, 7, 8 and 9 track||4′6
1 A line along that side of the flangeway which is nearer to the center of the track and at the same elevation as the gage line.
2 A line five-eighths of an inch below the top of the center line of the head of the running rail, or corresponding location of the tread portion of the track structure.