JOPLIN, Mo. — Flashing headlights can actually mean a few different things, depending on the context.

Fortunately, it only takes a second to check the two most common things the other driver is trying to communicate: Your own headlights, and the potential dangers ahead of you on the road (and despite what you may have heard, it’s not a gang initiation ritual.)

(Image courtesy: Getty Images)

But a quick flash of the headlights typically means the presence of law enforcement ahead, with radar, trying to catch speeders.

So the question becomes, is it legal to flash your headlights for this reason?

According to the Illinois Vehicle Code, it is not legal to flash your lights at another car to warn them of a speed trap. The rule reads: “Bright lights must be dimmed 500 feet before meeting an oncoming vehicle or 300 feet before passing a vehicle. Flashing or moving lights other than turn signals or hazard indicators are prohibited.”

The American Civil Liberties Union (ACLU), has stepped in numerous times across the country to represent individuals concerning this subject.

“The police cannot retaliate against drivers who have done nothing wrong and are simply exercising their right to communicate with other drivers,” says Jeffrey A. Mittman, executive director of the ACLU of Missouri.

Basically, every state has different rules regarding flashing lights as a warning. However, with the Supreme Court ruling in Spence v. Washington, it’s safe to say outdated municipal ordinances about this issue don’t hold water.