Trucks used primarily or regularly for the transportation of workmen shall be:
- (a) Equipped with seats securely fastened to the vehicle.
- (b) Equipped, if a motortruck, with a railing or other suitable enclosure on the sides and end of the vehicle not less than 46 inches above the floor of the vehicle.
- (c) Equipped with steps, stirrups, or other equivalent devices so placed and arranged that the vehicle may be safely mounted and dismounted.