I read years ago that animals catching food etc. are good at judging distances and intercepting prey up to the speed they can run. The article went onto say that a human can run at about 30kph max in a sprint so good at judging differences in relative speed up to about 30 kph but not so much if the speed is higher. It makes sense because I notice if doing 110kph on a highway and come up behind a truck/ grandmother or learner driver doing 80kph it is pretty easy to adjust to their speed, but if it is a tractor doing say 30kph so the difference is 80kph it is more of a shock to the system. So doing say 110kph and coming up to a Lambo doing zero is going to get you by surprise.
However I still agree you need to drive assuming someone has broken down just in front and be ready to take evasive action, the van driver was wrong for just driving along without being careful.
Back when I was about 19 or 20 I remember my sisters boyfriends car blowing both back tyres for some reason, and something went wrong with the suspension causing the back of the car to just hit the ground. The car stopped so quickly it was lucky no-one was behind us. I drive now expecting the car in front to have its suspension drop off and stop quickly as it lands on the ground.
