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 Delaware, the use of vehicle headlights must comply with Title 21, Section 4313 of the Delaware Code, which requires that drivers dim their high beams when approaching within 500 feet of an oncoming vehicle to avoid blinding the other driver. While the Delaware Code does not specifically address headlight flashing, tickets for this behavior could potentially be issued under the provisions related to the improper use of high beams or for aggressive driving if deemed appropriate by law enforcement. However, it's important to note that headlight flashing has been recognized in some jurisdictions as a form of speech protected under the First Amendment. This means that in certain cases, drivers have successfully challenged tickets for headlight flashing on constitutional grounds. The legality of headlight flashing for communication purposes, such as warning other drivers of hazards or police presence, can be subject to interpretation and may vary based on the specific circumstances of each case. Drivers in Delaware should exercise caution and consider the potential for misinterpretation or legal consequences when choosing to flash their headlights.