(4)The highway authority shall not ordinarily refuse permission to :(a)the erection of a building or structure or the making of or extending an excavation which conforms to the requirement of public health and welfare and of safety and convenience of traffic on the adjoining highway, or(b)the re-erection of a building or structure which was in existence on the date of which the restrictions under sub-section (1) came into force, unless such re-erection involved any material alteration to the outside appearance of the building or structure.
