Wig-wag (automobile)

A wig-wag is a device for flashing an automobile's headlights, so that only one of the two headlights operates at a time, with the two flashing at a preset rate. In its traditional form, a wig-wag emits the right and left headlights alternately, with each lamp usually lit for around half a second at a time.^{[citation needed]} In the United Kingdom, the wig-wag is only seen on the road on emergency vehicles. The 'standard' wig-wag is often used within a cycle of other illumination patterns, such as swiftly alternating the left and right headlights, alternating the left and right headlights slowly, or flashing both headlights together, and using a mixture of high- and low-beams.

Although the use of flashing headlights does increase the visibility of any vehicle,^{[citation needed]} it can also create problems. When high-beam headlights are flashed, the wig-wag may create glare or temporarily blind the drivers of oncoming vehicles.

Generally, wig-wags are prohibited on all vehicles except emergency vehicles.^[1] However, the road rules in New South Wales, Australia, and some areas in the United States allow school buses to have flashing headlights.^[2] In New South Wales specifically, additional wig-wag lights (separate from the headlights) are used on all public transport buses. In the United States, motorcycles are similarly allowed to be equipped with a headlamp modulator to increase visibility during the day. In the United States specifically, separate wig-wag lights are used on all public transport buses,^{[citation needed]} and such buses can use white or clear lights to increase visibility during the daytime.