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 Colorado, headlight flashing is not explicitly prohibited by state law, but drivers should be cautious as it could be interpreted under various traffic regulations. For instance, Colorado law requires that headlights must be dimmed when approaching within 500 feet of an oncoming vehicle or following within 300 feet of another vehicle (C.R.S. 42-4-217). While there is no specific statute against headlight flashing, it could potentially be considered under statutes related to the use of high beams or as a form of distraction to other drivers. Additionally, flashing headlights to warn drivers of speed traps could be seen as obstructing a police officer, although this interpretation is not clear-cut and could be subject to First Amendment protection as a form of communication. Drivers who have been ticketed for headlight flashing in Colorado or other states have sometimes successfully challenged such tickets on First Amendment grounds. However, outcomes can vary depending on the specific circumstances and the court's interpretation.