Why do some roads have those “squiggles” of tar instead of the entire road being black/grey from the tar?

Question

Why do some roads have those “squiggles” of tar instead of the entire road being black/grey from the tar?

In: Engineering

Answer 1

Those are from when they sealed a crack. If the whole road is covered, it’s from when they sealed it (the road) originally or recoated it.