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 Florida, headlight flashing is not illegal and is protected under the First Amendment as a form of communication. This was established following a 2012 court case where a judge ruled that drivers have the right to flash their headlights to warn other drivers of police speed traps. The Florida Department of Highway Safety and Motor Vehicles (DHSMV) and law enforcement agencies were subsequently instructed not to ticket drivers for flashing their headlights. While headlight flashing can be used for various reasons, such as warning of dangers on the road or signaling to other drivers, it should not be confused with the use of emergency vehicle lights, which are restricted to authorized vehicles. Florida law does require that headlights be used from sunset to sunrise, during any rain, smoke, or fog, and when visibility is less than 1000 feet, but the act of flashing headlights to communicate with other drivers is permissible.