- (1) Each end-facing exterior window of the trainset shall comply with the requirements for large object and ballistic impact scenarios as defined in this section.
(2) Each end-facing exterior window of the trainset shall demonstrate compliance with the following requirements for the large object impact test.
(i) The glazing article shall be impacted with a cylindrical projectile that complies with the following design specifications as depicted in Figure 1 to paragraph (b)(2)(i)(D) of this section:
- (A) The projectile shall be constructed of aluminum alloy such as ISO 6362-2:1990, grade 2017A, or its demonstrated equivalent;
- (B) The projectile end cap shall be made of steel;
- (C) The projectile assembly shall weigh 1 kilogram (kg) (−0, +0.020 kg) or 2.2 lbs (−0, +0.044 lbs) and shall have a hemispherical tip. Material may be removed from the interior of the aluminum portion to adjust the projectile mass according to the prescribed tolerance. The hemispherical tip shall have a milled surface with 1 mm (0.04 inches) grooves; and
(D) The projectile shall have an overall diameter of 94 mm (3.7 inches) with a nominal internal diameter of 70 mm (2.76 inches).

- (ii) The test of the glazing article shall be deemed satisfactory if the test projectile does not penetrate the glazing article, the glazing article remains in its frame, and the witness plate is not marked by spall.
- (iii) A new projectile shall be used for each test.
- (iv) The glazing article to be tested shall be that which has the smallest area for each design type. For the test, the glazing article shall be fixed in a frame of the same construction as that mounted on the vehicle.
- (v) A minimum of four tests shall be conducted and all must be deemed satisfactory. Two tests shall be conducted with the complete glazing article at 0 °C ± 0.5 °C (32 °F ± 0.9 °F) and two tests shall be conducted with the complete glazing article at 20 °C ± 5 °C (68 °F ± 9 °F). For the tests to be valid it shall be demonstrated that the core temperature of the complete glazing article during each test is within the required temperature range.
- (vi) The test glazing article shall be mounted at the same angle relative to the projectile path as it will be to the direction of travel when mounted on the vehicle.
- (vii) The projectile's impact velocity shall equal the maximum operating speed of the trainset plus 160 km/h (100 mph). The projectile velocity shall be measured within 4 m (13 feet) of the point of impact.
- (viii) The point of impact shall be at the geometrical center of the glazing article.
(3) Representative samples for large object impact testing of large end-facing cab glazing articles may be used, instead of the actual design size provided that the following conditions are met:
- (i) Testing of glazing articles having dimensions greater than 1,000 mm by 700 mm (39.4 by 27.6 inches), excluding framing, may be performed using a flat sample having the same composition as the glazing article for which compliance is to be demonstrated. The glazing manufacturer shall provide documentation containing its technical justification that testing a flat sample is sufficient to verify compliance of the glazing article with the requirements of this paragraph.
- (ii) Flat sample testing is permitted only if no surface of the full-size glazing article contains curvature whose radius is less than 2,500 mm (98 inches); and when a complete, finished, glazing article is laid (convex side uppermost) on a flat horizontal surface, the distance, (measured perpendicularly to the flat surface) between the flat surface and the inside face of the glazing article is not greater than 200 mm (8 inches).
(4) End-facing glazing shall demonstrate sufficient resistance to spalling, as verified by the large impact projectile test under the following conditions:
- (i) An annealed aluminum witness plate of maximum thickness 0.15 mm (0.006 inches) and of dimension 500 mm by 500 mm (19.7 by 19.7 inches) is placed vertically behind the sample under test, at a horizontal distance of 500 mm (19.7 inches) from the point of impact in the direction of travel of the projectile or the distance between the point of impact of the projectile and the location of the driver's eyes in the driver's normal operating position, whichever is less. The center of the witness plate is aligned with the point of impact.
- (ii) Spalling performance shall be deemed satisfactory if the aluminum witness plate is not marked.
- (iii) For the purposes of this part, materials used specifically to protect the cab occupants from spall (i.e., spall shields) shall not be required to meet the flammability and smoke emission performance requirements of § 299.413.
- (5) Each end-facing exterior window in a cab shall, at a minimum, provide ballistic penetration resistance that meets the requirements of appendix A to part 223 of this chapter.