N.J. Stat. Ann. § 39:3-64.3

At all times during the daylight or at night, whenever the driver of an itinerant vendor's vehicle shall stop or park the vehicle on any roadway or the shoulder thereof for the purpose of transacting business, he shall immediately flash the 2 front and 2 rear turn signals of the vehicle simultaneously as a vehicular traffic hazard warning signal and continue such flashing so long as the vehicle remains stopped or parked for such purpose.