MSHA - Code of Federal Regulations - 30 CFR 57.14106
30 CFR § 57.14106
Falling object protection.
(a) Fork-lift trucks, front-end loaders, and bulldozers shall be
provided with falling object protective structures if used in an area where
falling objects could create a hazard to the operator.
(b) The protective structure shall be capable of withstanding the
falling object loads to which it could be subjected.