Civil Engineers in road and infrastructure work - What's the deal with the random slits that you see getting cut in existing roads?

I have to travel a bit for work via car and I've always wondered even on existing roads that have been around for years; you'll go out and see them cutting a set of uniform slits and then filling them in with asphalt even on concrete roads.

These sometimes are restricted to a single lane on a dual lane highway, or can span multiple lands on a highway. The width of the cuts are either the size or 2 or so tire widths, or 1.5 - 2 car lengths. They will be uniformly spaced out on the road. with 100s of them in a section.

It doesn't look like it's for utility work or road repair. What are they doing?