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 Montana, headlight flashing is not explicitly addressed in the state statutes as a distinct traffic violation. However, Montana law does regulate the use of high beam headlights: drivers must dim their high beams when approaching an oncoming vehicle within 500 feet or when following a vehicle within 300 feet. Violating these regulations could potentially result in a traffic citation. While headlight flashing could be interpreted under these or other general traffic provisions, such as those pertaining to the use of vehicle lights, the act of flashing headlights to communicate with other drivers is not directly prohibited. Additionally, there have been instances where drivers have contested tickets for headlight flashing on the basis of the First Amendment, arguing that it constitutes protected speech. Courts have varied in their responses to such challenges, and the outcome can depend on the specific circumstances of each case and the interpretation of the First Amendment in this context. It's important for drivers in Montana to be aware of the general rules regarding headlight use and to exercise caution when choosing to flash their headlights, as it could be misinterpreted or lead to unintended legal consequences.