12. The vehicle shall be examined to ascertain whether its exhaust system complies with the exhaust requirements and in particular to ascertain whether—
(a)where the vehicle is propelled by means of an internal combustion engine, it is equipped with a silencer, expansion chamber or other contrivance suitable and sufficient for reducing as far as may be reasonable the noise caused by the escape of the exhaust gases from the engine, and
(b)all parts of the exhaust system with which the vehicle is equipped as aforesaid are in a good and efficient condition.