The interior and exterior parts of all passenger-carrying amusement devices with which a passenger may come in contact shall be smooth and rounded, free from sharp, rough or splintered edges and corners, with no protruding studs, bolts, screws or other projections which might cause injury. Interior parts upon or against which a passenger may be forcibly thrown by the action of the amusement device shall be adequately padded. Devices which are self-powered and which are operated by a passenger shall have the driving mechanism so guarded and the guards so locked in place as to prevent passengers from gaining access to the mechanism. Such belts, bars, foot rests and other equipment as may be necessary for safe entrance and exit and for support while the device is in operation shall be provided. Such equipment and the fastenings thereof shall be of sufficient strength to retain the passengers. The fastenings shall be of a type which cannot be inadvertently released.