this is odd, but somehow Steve researched and found out what this was all about! This was a roadside warning sign on the road near Lake Balaton near the town of Lepsény, Hungary

 

https://www.jalopyjournal.com/forum/threads/vintage-shots-from-days-gone-by-part-2.1154030/page-1251#post-14108757

The sign "Lassu hajtas vagy gyászszertartás" literally translated says: "Slow drive or mourning ceremony" while colloquially we'd say "Slow down or it's your funeral."

thanks Steve!