&quot; If something can enter the road and you can&#x27;t stop in time then you have already failed. Driver-less cars should never drive at a speed where they can&#x27;t stop in time.&quot;<p>So, what happens if something blows into or falls on a motorway?  A car hurtling down the road at 70mph is going to have a hell of a time stopping for an unexpected obstacle, human controlled or otherwise.