SECTION 7. Right of way of fire engines, patrol vehicles and ambulances; obstruction; penalties

The members and apparatus of a fire department while going to a fire or responding to an alarm, police patrol vehicles and ambulances, and ambulances on a call for the purpose of hospitalizing a sick or injured person shall have the right of way through any street, way, lane or alley. Whoever wilfully obstructs or retards the passage of any of the foregoing in the exercise of such right shall be punished by a fine of fifty dollars or by imprisonment for not more than three months for the first offense and by a fine of not more than five hundred dollars or by imprisonment for up to one year for a second and subsequent offenses; provided, however, that for a third or subsequent offense the court or the registry of motor vehicles, in addition to any such fine or imprisonment, may suspend the license of the person so convicted and may order mandatory classroom retraining in motor vehicle and traffic laws.