49 C.F.R. § 238.427 Suspension system.
Title 49 - Transportation
(a) General requirements. (1) Suspension systems shall be designed to reasonably prevent wheel climb, wheel unloading, rail rollover, rail shift, and a vehicle from overturning to ensure safe, stable performance and ride quality. These requirements shall be met: (i) In all operating environments, and under all track conditions and loading conditions as determined by the operating railroad; and (ii) At all track speeds and over all track qualities consistent with the Track Safety Standards in part 213 of this chapter, up to the maximum operating speed and maximum cant deficiency of the equipment. (2) Passenger equipment shall meet the safety performance standards for suspension systems contained in appendix C to this part, or alternative standards providing at least equivalent safety if approved by FRA under the provisions of §238.21. (b) Car body accelerations. (1) A passenger car shall not operate under conditions that result in a steady-state lateral acceleration greater than 0.12g as measured parallel to the car floor inside the passenger compartment. During pre-revenue service acceptance testing of the equipment under §238.111 and §213.345 of this chapter, a passenger car shall demonstrate that steady-state lateral acceleration does not exceed 0.1g at the maximum intended cant deficiency. (2) While traveling at the maximum operating speed over the intended route, the train suspension system shall be designed to: (i) Limit the vertical acceleration, as measured by a vertical accelerometer mounted on the car floor, to no greater than 0.55g single event, peak-to-peak over a one second period; (ii) Limit lateral acceleration, as measured by a lateral accelerometer mounted on the car floor, to no greater than 0.3g single event, peak-to-peak over a one second period; and (iii) Limit the combination of lateral acceleration (aL) and vertical acceleration (aV) occurring over a one second period as expressed by the square root of (aL2 +aV2 ) to no greater than 0.6g, where aL may not exceed 0.3g and aV may not exceed 0.55g. Compliance with the requirements of paragraph (b)(2) shall be demonstrated during the pre-revenue service acceptance testing of the equipment required under §238.111 and §213.345 of this chapter. (3) For purposes of this paragraph: (i) Car body acceleration measurements shall be processed through a filter having a cut-off frequency of 10 Hz; and (ii) Steady-state lateral acceleration shall be computed as the mathematical average of the accelerations in the body of a curve, between the spiral/curve points. In a compound curve, steady-state lateral acceleration shall be measured separately for each curve segment. (c) Truck (hunting) acceleration.Each truck shall be equipped with a permanently installed lateral accelerometer mounted on the truck frame. The accelerometer output signals shall be processed through a filter having a band pass of 0.5 to 10 Hz to determine if hunting oscillations of the truck are occurring. If hunting oscillations are detected, the train monitoring system shall provide an alarm to the operator, and the train shall be slowed to a speed at least 5 mph less than the speed at which the hunting oscillations stopped. For purposes of this paragraph, hunting oscillations are considered a sustained cyclic oscillation of the truck which is evidenced by lateral accelerations in excess of 0.4g root mean square (mean-removed) for 2 seconds. (d) Overheat sensors. Overheat sensors for each wheelset journal bearing shall be provided. The sensors may be placed either onboard the equipment or at reasonable intervals along the railroad's right-of-way. [64 FR 25660, May 12, 1999, as amended at 67 FR 19992, Apr. 23, 2002]
Title 49: Transportation
PART 238—PASSENGER EQUIPMENT SAFETY STANDARDS
Subpart E—Specific Requirements for Tier II Passenger Equipment
§ 238.427 Suspension system.
