49 CFR 213.55: Track alinement.

(a) Except as provided in paragraph (b) of this section, alinement may not deviate from uniformity more than the amount prescribed in the following table:

Class of track Tangent track Curved track

The deviation of the mid-offset from a 62-foot line 1 may not be more than—(inches) The deviation of the mid-ordinate from a 31-foot chord 2 may not be more than—(inches) The deviation of the mid-ordinate from a 62-foot chord 2 may not be more than—(inches)

Class 1 track 5 3 N/A 5

Class 2 track 3 3 N/A 3

Class 3 track 13⁄4 11⁄4 13⁄4

Class 4 track 11⁄2 1 11⁄2

Class 5 track 3⁄4 1⁄2 5⁄8

1 The ends of the line shall be at points on the gage side of the line rail, five-eighths of an inch below the top of the railhead. Either rail may be used as the line rail; however, the same rail shall be used for the full length of that tangential segment of the track.

2 The ends of the chord shall be at points on the gage side of the outer rail, five-eighths of an inch below the top of the railhead.

3 N/A—Not Applicable

(b) For operations at a qualified cant deficiency, Eu, of more than 5 inches, the alinement of the outside rail of the curve may not deviate from uniformity more than the amount prescribed in the following table:

Class of track Curved track

The deviation of the mid-ordinate from a 31-foot chord 1 may not be more than—(inches) The deviation of the mid-ordinate from a 62-foot chord 1 may not be more than—(inches)

Class 1 track 2 3 N/A 11⁄4

Class 2 track 2 3 N/A 11⁄4

Class 3 track 3⁄4 11⁄4

Class 4 track 3⁄4 7⁄8

Class 5 track 1⁄2 5⁄8

1 The ends of the chord shall be at points on the gage side of the outer rail, five-eighths of an inch below the top of the railhead.

2 Restraining rails or other systems may be required for derailment prevention.

3 N/A—Not Applicable