Section 50. (a) The armed forces of the United States and any part of the armed forces of the commonwealth parading or performing any duty according to law shall have the right of way in any street or highway through which they may pass, and drivers of military vehicles may drive such vehicles through an intersection of ways contrary to any traffic signs or signals regulating traffic at such intersection, if a police officer or duly authorized member of the military service is stationed at the intersection to regulate traffic; provided, that the carriage of the United States mails, the legitimate functions of the police and the progress and operation of fire departments shall not be disrupted. Motor vehicles of the armed forces of the commonwealth may be equipped with sirens or other audible warning devices and with visible warning devices as provided in section 7E of chapter 90.

(b) A vehicle owned or operated by a designated member of the armed forces of the commonwealth who is assigned public safety duties that require immediate emergency response to incidents or events, such as emergency response to hazardous materials or weapons of mass destruction incidents may, with prior written authorization by the adjutant general, and only by authority of a permit issued by the registrar of motor vehicles, have mounted thereon flashing, rotating or oscillating red lights. Said emergency lights may only be activated when circumstances reasonably require an immediate emergency response. Upon termination of the duties which warranted the issuance of the permit, the adjutant general shall immediately notify in writing the registrar of motor vehicles who shall forthwith revoke such red light permit. Upon revocation, the registrar of motor vehicles shall notify the owner and operator of the vehicle for which such permit was issued and the owner and operator shall thereafter be subject to a fine of not less than $100 nor more than $300, unless otherwise provided.