Exemptions. Subsection
A of this section shall not apply to heavy commercial vehicles going to or coming from places upon said streets for the purpose of making deliveries of goods, materials or merchandise to or similar collections from abutting land or buildings or adjoining streets or ways to which access cannot otherwise be gained; or to vehicles used in connection with the construction, maintenance and repair of said streets or public utilities therein; or to federal, state, municipal or public service corporation owned vehicles.