No provision of this chapter shall apply to any of the following:

A. Motor vehicles used exclusively to convey children to and from schools; provided, that such vehicles shall, notwithstanding the provisions of this section, be subject to all of the safety provisions of this chapter or that may be prescribed by the commission;

B. United States mail carriers when not engaged in other business as common carriers of passengers;

C. Intercity buses operating principally outside the city limits and operating under permits from the state;

D. Buses traveling on fixed routes and operated under special authority or franchise of the city;

E. Mortuary and ambulance services.

(Prior code § 18-4).