Here's What It Actually Means When Someone Flashes Their Headlights at You
You're driving down the road at night, and someone flashes their headlights at you--maybe a quick off-and-on, or they flicker their high beams. Or, even more perplexingly, they do this in broad daylight. What does it mean? (And no, it's not a gang initiation ritual.)
Flashing headlights can actually mean a few different things, depending on the context. Fortunately it only takes a second to check the two things the other driver might be trying to alert you to: your own headlights, and potential dangers ahead of you in the road.
Check your headlights
If you're driving at night and you forgot to turn your headlights on, a friendly flash of the headlights is how another driver can tell you "turn your lights on, dummy."
If your lights are already on, it's possible they're letting you know that you left your high beams on. Remember, your "high beams" or "brights" are for illuminating the empty road in front of you, and you should switch back to regular headlights when other drivers approach. Most states require that you turn off your brights if you are within 500 feet of an approaching car or 200-300 feet of a car you are following.
Watch for surprises
If your headlights are operating properly, or if you're driving in the daytime, that approaching car is probably trying to warn you about something ahead. Often that's a speed trap: a police car waiting by the side of the road to pull over speeding drivers. With the advance warning, you can slow down and avoid getting caught.
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Even if it's not a speed trap, take the flash as advice to slow down and pay attention to your surroundings. Where I am, in Pennsylvania, the next most likely probability is that there is a deer trying to cross the road. A flash of the headlights would also be the way you'd warn drivers about debris in the road, or a person trying to cross--anything they may have seen that they want to make sure you see, too.
Bonus: "You can go now."
There's another use for a quick friendly flash of the lights, and that's to signal another driver that they can take their turn on the road.
For example, if you're trying to pull out of a driveway onto a busy road, one of the cars coming down the way may slow down to give you space to pull out. A blink of the lights lets you know they're slowing down on purpose, and will wait for you to make your move.
Or let's say you roll up to a stop sign at roughly the same time as another car. They may flash their lights to say "you go first," so you're not sitting there waiting for each other. In my hometown, we have a more formalized version of this: the infamous "Pittsburgh left." If you're at a red light and waiting to turn left, the car that is facing you and going straight may decide to let you make your turn first. If they flash their lights while the light is still red, they're letting you know that you can go as soon as the light is green.
Here's a time that you can flash your lights to help someone out: When a big semi truck is trying to change into your lane on a busy road, they can't always judge the distance behind them accurately. You can flash your lights to say "You have the room, go ahead," and they'll pull in ahead of you. Sometimes they'll even respond by activating the blinky lights on the back of their truck as a thank you.