The reflective studs, commonly known as 'Cat's Eyes', in the centre line of the road have been removed to enable re-surfacing to take place.
These passive devices are being replaced by solar powered LED models.
The edges of some roads are marked by green (nearside) or red (offside) cat's eyes.
I've driven quite a bit in the US but mostly by day, so I don't recall seeing them there.
Are they part of the road fixtures and fittings?
In my defence, it's twelve years since I was there and the memory does tend to fade.
Link.