It’s a sign you are suppose to wear behind anything that might stick out of the back of your car.
Apperantly some new eu regulation. Just one small issue. The signs looks slightly different in each country and you need to have their own one. Stupid!
Perfect example of overregulation.
My mission now is to find one that is accepted in Italy since that’s where I’m headed. I want to absorb some Italian culture and style. That might make me even cooler ☺