49 CFR § 299.311 Track geometry; general - Code of Federal Regulations

If the values listed in the following table are exceeded, the railroad shall initiate remedial action. A reduction in operating speed so that the condition complies with the limits listed for a lower speed shall constitute bringing the track into compliance.

Table 1 to § 299.311

Track geometry parameter (millimeter (mm))	Track class	H0	H1	H2	H3	H4	H5	H6	H7
Gauge is measured between the heads of the rails at right angles to the rails in a plane 14 mm (0.55 inches) below the top of the rail head and may not exceed -	Min.	1429	1429	1429	1429	1429	1429	1429	1429
	Max.	1454	1454	1454	1454	1454	1454	1454	1454
The deviation from uniformity ¹ of the mid-chord offset on either rail for a 10 meter (m) chord (alignment) may not be more than -	10 m chord	38	31	31	14	12	10	8	7
The deviation from uniform profile on either rail at the mid-ordinate of a 10 m chord (surface) may not be more than -	10 m chord	40	40	40	27	22	18	15	13
The deviation from uniform crosslevel at any point on tangent and curved track may not be more than -		50	26	26	22	18	14	9	9
The difference in crosslevel between any two points 2.5 meters (8.2 feet) apart (twist) may not be more than -	2.5 m	26	26	26	22	18	14	9	9

¹ Uniformity for alignment at any point along the track is established by averaging the measured mid-chord offset values for a 10 m (32.8 feet) chord for nine consecutive points that are centered around that point and spaced at 2.5 m (8.2 feet) intervals.

Title 49

SECTION 299.311

299.311 Track geometry; general.