49 C.F.R. § 213.57 : Transportation — OTHER REGULATIONS RELATING TO TRANSPORTATION — FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION — TRACK SAFETY STANDARDS — TRACK GEOMETRY — Curves; elevation and speed limitations

(a) The maximum elevation of the outside rail of a curve may not be more than 8 inches on track Classes 1 and 2, and 7 inches on track Classes 3 through 5. The outside rail of a curve may not be lower than the inside rail by design, except when engineered to address specific track or operating conditions; the limits in §213.63 apply in all cases.
(b) The maximum allowable posted timetable operating speed for each curve is determined by the following formula-

Where-

Vmax = Maximum allowable posted timetable operating speed (m.p.h.).

Ea = Actual elevation of the outside rail (inches).1

1 Actual elevation, Ea , for each 155-foot track segment in the body of the curve is determined by averaging the elevation for 11 points through the segment at 15.5-foot spacing. If the curve length is less than 155 feet, the points are averaged through the full length of the body of the curve.

Eu = Qualified cant deficiency 2 (inches) of the vehicle type.

2 If the actual elevation, Ea , and degree of curvature, D, change as a result of track degradation, then the actual cant deficiency for the maximum allowable posted timetable operating speed, Vmax , may be greater than the qualified cant deficiency, Eu . This actual cant deficiency for each curve may not exceed the qualified cant deficiency, Eu , plus 1 inch.

D = Degree of curvature (degrees).3

3 Degree of curvature, D, is determined by averaging the degree of curvature over the same track segment as the elevation.

(c) All vehicles are considered qualified for operating on track with a cant deficiency, E u , not exceeding 3 inches. Table 1 of appendix A to this part is a table of speeds computed in accordance with the formula in paragraph (b) of this section, when E u equals 3 inches, for various elevations and degrees of curvature.
(d) Each vehicle type must be approved by FRA to operate on track with a qualified cant deficiency, E u , greater than 3 inches. Each vehicle type must demonstrate, in a ready-for-service load condition, compliance with the requirements of either paragraph (d)(1) or (2) of this section.
(1) When positioned on a track with a uniform superelevation equal to the proposed cant deficiency:
(i) No wheel of the vehicle type unloads to a value less than 60 percent of its static value on perfectly level track; and
(ii) For passenger cars, the roll angle between the floor of the equipment and the horizontal does not exceed 8.6 degrees; or
(2) When operating through a constant radius curve at a constant speed corresponding to the proposed cant deficiency, and a test plan is submitted to and approved by FRA in accordance with §213.345:
(i) The steady-state (average) load on any wheel, throughout the body of the curve, is not less than 60 percent of its static value on perfectly level track; and
(ii) For passenger cars, the steady-state (average) lateral acceleration measured on the floor of the carbody does not exceed 0.15g.
(e) The track owner or railroad shall transmit the results of the testing specified in paragraph (d) of this section to FRA's Associate Administrator for Railroad Safety/Chief Safety Officer (FRA) requesting approval for the vehicle type to operate at the desired curving speeds allowed under the formula in paragraph (b) of this section. The request shall be made in writing and contain, at a minimum, the following information-
(1) A description of the vehicle type involved, including schematic diagrams of the suspension system(s) and the estimated location of the center of gravity above top of rail;
(2) The test procedure, 4 including the load condition under which the testing was performed, and description of the instrumentation used to qualify the vehicle type, as well as the maximum values for wheel unloading and roll angles or accelerations that were observed during testing; and

4 The test procedure may be conducted whereby all the wheels on one side (right or left) of the vehicle are raised to the proposed cant deficiency, the vertical wheel loads under each wheel are measured, and a level is used to record the angle through which the floor of the vehicle has been rotated.

(3) For vehicle types not subject to parts 229 or 238 of this chapter, procedures or standards in effect that relate to the maintenance of all safety-critical components of the suspension system(s) for the particular vehicle type. Safety-critical components of the suspension system are those that impact or have significant influence on the roll of the carbody and the distribution of weight on the wheels.
(f) In approving the request made pursuant to paragraph (e) of this section, FRA may impose conditions necessary for safely operating at the higher curving speeds. Upon FRA approval of the request, the track owner or railroad shall notify FRA in writing no less than 30 calendar days prior to the proposed implementation of the approved higher curving speeds allowed under the formula in paragraph (b) of this section. The notification shall contain, at a minimum, identification of the track segment(s) on which the higher curving speeds are to be implemented.
(g) The documents required by this section must be provided to FRA by:
(1) The track owner; or
(2) A railroad that provides service with the same vehicle type over trackage of one or more track owner(s), with the written consent of each affected track owner.
(h)
(1) Vehicle types permitted by FRA to operate at cant deficiencies, E u , greater than 3 inches but not more than 5 inches shall be considered qualified under this section to operate at those permitted cant deficiencies for any track segment. The track owner or railroad shall notify FRA in writing no less than 30 calendar days prior to the proposed implementation of such curving speeds in accordance with paragraph (f) of this section.
(2) Vehicle types permitted by FRA to operate at cant deficiencies, E u , greater than 5 inches shall be considered qualified under this section to operate at those permitted cant deficiencies only for the previously operated or identified track segments(s).
(i) For vehicle types intended to operate at any curving speed producing more than 5 inches of cant deficiency, the following provisions of subpart G of this part shall apply: §§213.333, 213.345, and 213.369.
(j) As used in this section-
(1) Vehicle means a locomotive, as defined in §229.5 of this chapter; a freight car, as defined in § 215.5 of this chapter; a passenger car, as defined in §238.5 of this chapter; and any rail rolling equipment used in a train with either a freight car or a passenger car.
(2) Vehicle type means like vehicles with variations in their physical properties, such as suspension, mass, interior arrangements, and dimensions that do not result in significant changes to their dynamic characteristics.

49 C.F.R. § 213.57

78 FR 16101, 3/13/2013