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 Michigan, headlight flashing is not explicitly prohibited by state law, but it can be subject to interpretation under various traffic regulations. For instance, Michigan Vehicle Code (MCL 257.700) states that headlights must be dimmed when approaching within 500 feet of an oncoming vehicle or following within 200 feet of another vehicle. While this law does not directly address headlight flashing, it does regulate the use of high beams, which could be related to the practice. Additionally, flashing lights are generally reserved for emergency vehicles and certain service vehicles according to MCL 257.698, which could potentially be applied to non-emergency vehicles using flashing headlights. However, drivers in Michigan have sometimes contested tickets for headlight flashing on the grounds that it constitutes protected speech under the First Amendment. Courts have varied in their rulings on this issue, and the legality of headlight flashing can depend on the specific circumstances and the interpretation of local ordinances and state statutes.