Headlight flashing is the act of a driver flashing their headlights at an oncoming driver by briefly turning the headlights on or off, or from high beam to low beam, or low beam to high beam. There is no set or clear message transmitted by headlight flashing, but it often means the driver who flashes their headlights believes the oncoming driver’s headlights are inappropriately on high beams or are not turned on or illuminated when they should be.

Headlight flashing may also be intended to convey other messages, such as warning another driver of the flashing driver’s presence; telling another driver to proceed in front of the flashing driver (yielding the right of way); or warning an oncoming driver of danger ahead—which may include a deer or other animal in the road, an automobile wreck, or a police officer hidden from view who is checking the speed of passing drivers and issuing speeding tickets (a speed trap).

Police officers have sometimes issued traffic tickets to drivers for headlight flashing, and in some instances a traffic stop for headlight flashing has led to more serious charges and an arrest for DUI/DWI, for example. Tickets for headlight flashing are often issued based on an alleged violation of a municipal ordinance or a state statute that prohibits:

• high beam headlights within a certain distance (500 feet, for example) of an oncoming driver;

• aggressive driving;

• having flashing lights on a vehicle; or

• obstructing a police investigation.

Drivers who have received tickets for headlight flashing have sometimes challenged the ticket—or the traffic stop that led to an arrest and additional charges—on the ground that headlight flashing is a communication protected by the First Amendment to the United States Constitution.

Laws and ordinances vary from state to state and among cities and towns (municipalities), and state and federal courts have arrived at different conclusions when applying the First Amendment and other laws and ordinances to traffic tickets or stops based on headlight flashing.

In Idaho, the regulation of headlight flashing can be influenced by various traffic laws. While there is no specific Idaho statute that directly addresses the act of headlight flashing, drivers could potentially be cited under statutes that regulate the use of high beam headlights, such as Idaho Code § 49-903, which requires drivers to dim their high beams when approaching another vehicle within 500 feet. Additionally, headlight flashing could be interpreted under laws related to aggressive driving or the prohibition of flashing lights on certain vehicles, as per Idaho Code § 49-910 and § 49-914. However, it's important to note that headlight flashing has been argued in some jurisdictions as a form of speech protected under the First Amendment. The outcomes of such challenges can vary, and while some courts have upheld the right to flash headlights as a form of communication, others have allowed citations to stand based on specific traffic safety statutes. Drivers in Idaho should be aware that while headlight flashing is not explicitly banned, it could lead to traffic stops or citations under related traffic laws, and the interpretation of these actions may depend on the context and the discretion of law enforcement.