The driver may then fail to realize that the car ahead is stopped until it is too late. One way that drivers we judge their own speed is by their movement relative to objects in the visual field. When driving fast, for example, telephone poles on the side of the road zip by. The driver in our example will likely misjudge the time it would take to stop. People automatically perceive objects which are low contrast and indistinct as being further away.
Distant objects are then less indistinct and fainter.
The driver approaching the stopped car will judge it to be further away than it really is and therefore underestimate the time and distance needed to stop. References Green, M. Contrast detection and direction discrimination of drifting gratings.