Headlight flashing

Headlight flashing is the act of either briefly switching on the headlights of a car, or of momentarily switching between a headlight's high beams and low beams, in an effort to communicate with another driver or drivers. The signal is sometimes referred to in car manufacturers' manuals as an optical horn, since it draws the attention of other drivers.

The signal can be intended to convey a variety of messages, including a warning to other drivers of road hazards or of speed traps, and it can also be a form of aggressive driving. The legality of headlight flashing varies by jurisdiction.

Headlight flashing might have come into more common use as a means of attempting driver-to-driver communication by the mid-1970s, when cars began to come with headlight beam selectors located on the steering column—typically activated by pulling the turn signal stalk—rather than the previous foot-operated pushbutton switches. The signal stalk configuration was later wired to permit the momentary activation of the high beams regardless of whether the headlamp switch was turned on or off.

In the most basic sense, headlight flashing is a way of attracting attention, for any of a number of purposes. In this way, it can be perceived as the visual equivalent of blowing the horn, again for any of a number of reasons. This equivalency is underscored by some car owner's manuals, which identify the steering column control lever which allows headlight flashing as the "optical horn". Headlight flashing can be used simply to let other drivers know of one's presence, or as a response to acknowledge the presence or actions of other drivers. Some drivers flash their headlights as a signal that they are yielding the right of way to another driver, for example at an intersection controlled by stop signs.

Headlight flashing is commonly used to warn other drivers of dangers on the road, such as crashed cars or police speed traps. Headlight flashing can be used to give thanks to another driver. For example, in situations where a driver is warned of police activity in the area, it is sometimes considered courteous to flash one's own lights in response.

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Wikipedia