(a) The maximum elevation of the outside rail of a curve may not be more than 200 mm (7-7/8 inches). 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 § 299.311 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 (km/h).
Ea = Actual elevation of the outside rail (mm). Actual elevation, Ea, for each 50-meter track segment in the body of the curve is determined by averaging the elevation for 11 points through the segment at 5-meter spacing. If the curve length is less than 50-meters, average the points through the full length of the body of the curve.
Eu = Qualified cant deficiency (mm) of the vehicle type.
R = Radius of curve (m). Radius of curve, R, is determined by averaging the radius of the curve over the same track segment as the elevation.
(c) All vehicles are considered qualified for operating on track with a cant deficiency, Eu, not exceeding 75 mm (3 inches).
(d) Each vehicle type must be approved by FRA, under § 299.609, to operate on track with a qualified cant deficiency, Eu, greater than 75 mm (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 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 and approved by FRA in accordance with § 299.609(d)—
(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 railroad shall transmit the results of the testing specified in paragraph (d) of this section to FRA in accordance with §§ 299.9 and 299.613 requesting approval under § 299.609(g) 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 shall 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; and
(2) The test procedure, 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.
Note 1 to paragraph (e)(2):
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 and lowered, and then 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.
(f) Upon FRA approval of the request to approve the vehicle type to operate at the desired curving speeds allowed under the formula in paragraph (b) of this section, the railroad shall notify FRA in accordance with § 299.9 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) As used in this section, and § 299.609, 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.