Is it Illegal in NH to Flash Your Lights to Warn of Police Activity?

It happened on a two-lane town road in New Hampshire.

I had just passed a speed trap in a small town.  A local police officer had set up radar in the school parking lot after hours and was checking the local speeds, which were posted.

After I passed the police activity, I flashed my headlights to an oncoming vehicle to make them aware of what was ahead.  This is common knowledge in New England, and while it is old school, it still happens often.

What happened next, I did not expect.

The oncoming car was a police truck (unknown by me), so when I flashed my headlights, he turned on his lights... and siren momentarily.

It was his way of saying don't do that.

This shocked me as he passed me shaking his head.  Then it occurred to me, am I doing something illegal?

The short answer is no, it is not illegal, but there are other things to consider.

According to yourmechanic.com, in New Hampshire, "High beams must be dimmed when within 150 feet of another vehicle".   So, technically, you can be stopped for having your high beams on closer than 150 feet of the oncoming vehicle, even if you are simply flashing your lights.

This might sound like a stretch, but is it worth it to hire an attorney to fight this in court?

Motorbiscuit.com says it goes against our First Amendment right of Freedom of Speech to be fined for flashing your headlights, but there have been instances in some states where a citation was issued because it was deemed an obstruction of justice.

Here's an alternative.  Download a map app, like Waze or Google Maps, which now offers real time locations of all construction and police stops.