§ 299.401 Clearance requirements.
(a) General. The rolling stock shall be designed to meet all applicable clearance requirements of the railroad. The railroad shall make its clearance diagrams available to FRA upon request.
(b) Clearance above top of rail. No part or appliance of a trainset except the wheels, sander tips, wheel guards, and other components designed to be in the path of the wheel (i.e., above the rail and aligned inside the wheel width path) may be less than 60 mm (2.36 inches) above the top of rail.
(c) Obstacle deflector. The leading end of a trainset shall be equipped with an obstacle deflector that extends across both rails of the track. The minimum clearance above the rail of the obstacle deflector shall be 76 mm (3 inches), and the maximum clearance shall be 229 mm (9 inches).
(d) Flexible wheel guards. The lead axle of a trainset shall be equipped with flexible wheel guards mounted on the bogie below the primary suspension with a maximum clearance above the rail of 15 mm (0.59 inches).