Cat's eyes

In Britain, roads have a row of studs down the middle with little reflective patches on them. At night, the headlamps of cars pick the studs out and so the driver can tell where the middle of the road is. They look a bit like cat's eyes when they are caught in a beam of light.

This is a fact that Europeans who chortle at British road chaos when it snows are generally not aware of. Especially since it means you can't just scrape all the snow & ice off the road surface with a snowplough without ripping up all the studs as well.