49 CFR 213.143 - 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
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 -
|Guard face gage
The distance between guard lines 1, measured across the track at right angles to the gage line 2, may not be more than -
|Class 1 track||4′6
|Class 2 track||4′6
|Class 3 and 4 track||4′ 6
|Class 5 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 5/8 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.