Memory of the road
During a drive to work this morning, I had an interesting realization. At several points along the way, I had to break sharply, to maintain distance in front of the car ahead.
Why were they braking?
Precisely the same reason I assume.
In all likelihood the real danger was long gone.
So long as the quantity of traffic stays at a sufficient level, such as on a highway like SR520; these artifacts can potentially last for hours.
The memory of the road.