The provisions of this Part do not apply to the driver of--
(a) any motor vehicle while conveying a police officer on urgent duty, or
(b) any fire engine or appliance while proceeding to a fire, or
(c) any ambulance while proceeding to the scene of an accident or to a hospital with an injured person, or
(d) any vehicle referred to in paragraph (a), (b) or (c) while proceeding to any place to deal with an emergency,if the observance of those provisions would be likely to hinder the vehicle while so doing.