Punitive damages are only awarded to an injured plaintiff when the wrongful behavior of the defendant was despicable or reprehensible. A common scenario where punitive damages are awarded arises when a defendant is found guilty of wanton or malicious acts or of fraud.
Wikipedia has an article on: speed cushion. Wikipedia. speed cushion (plural speed cushions) A form of speed bump, often one of a series, that allows larger (especially emergency) vehicles to straddle them without slowing down.
Hitting an immovable object, such as a wall, the speed of the car would have to be 10-15mph. I suppose the difference would be that hitting the wall would be instantaneous deceleration, whilst hitting another vehicle would give a cushioning effect. Its not really a case of How fast but more a case of how hard. For example an air bag will deploy in the case of a stationary car being hit by a lorry at 5mph.