Every stop lamp shall be so constructed, placed and used as to indicate by a substantial increase in illumination that the service brakes of the vehicle have been applied, except as otherwise provided in this section. Stop lamps are not required to be lighted when the emergency feature of trailer brakes is activated by means of either manual or automatic control on the towing vehicle. Stop lamps on a towing vehicle need not be lighted when service brakes are applied to the towed vehicle or vehicles only. No stop lamp need be lighted as such when it is in use as a turn signal or when it is turned off by the turn signal switch as provided in paragraph (b) of section 8 of this act.

L.1964, c. 136, s. 9.