I think the current powers that be hold clean air and safe roads in the same esteem as they hold education and research.
Maybe "Support for education and research should be as fundamental as golf tournaments or Diet Coke" would be a better anology.
Background radiation is a thing.
Granite and bananas are a tiny bit more radioactive than typical things, without making them dangerous.
- Florida is using photogypsum - https://www.ijpr.org/npr-news/2023-06-30/florida-moves-forwa...
- Photogypsum in the US is banned if it radiates at >0.4 Bq/g of 226 Ra. https://en.wikipedia.org/wiki/Phosphogypsum
- Granite radiates at maybe 450 Bq/kg -> 0.45 Bq/g of 226 Ra. https://www.nature.com/articles/jes200944
So it looks like we're dealing with pretty standard rock. If this stuff was going to be banned without special permitting it is probably a little more risky than a granite kitchen-top counter if someone goes and sits on the road all day. Although this all raises the question of whether granite should be legal as a building material given that people get twitchy about this stuff - I doubt anyone can prove that granite is safe in this context.
I'd be more worried about testing phosphogypsum's mechanical properties before anyone starts testing the radioactive ones. And danger relative to tyre rubber; although that has probably already been studied somewhere since it is an obvious thing to check.