Sentence:  ... Claxton flipped on the flashing red and blue <WSD>wigwag</WSD> lights on his patrol car's front bumper. ... And the truck, apparently responding to the flashing <WSD>wigwag</WSD> lights, edged farther off the pavement onto the shoulder and stopped; properly, cooperatively, deceptively. 
Meaning of the word marked with <WSD> tags:  A device used to cause lamps installed on a motor vehicle, especially an emergency vehicle such as an ambulance or police car, to flash as a warning.