And in my experience, a key effect of speed limits is that when you're driving that slowly, you're more likely to be daydreaming because there's (99.9% of the t

And in my experience, a key effect of speed limits is that when you're driving that slowly, you're more likely to be daydreaming because there's (99.9% of the time) no reason to pay attention. And that 1-in-a-thousand time in your induced daydream is when you really needed to be paying attention. In other words, higher velocities have longer stopping distances from a purely Newtonian perspective. But from a human factors perspective, making the job boring impairs the operator's reactions, also causing longer stopping distances. Obligatory anecdote: over last summer a new family moved in down the street, put up their own "no speeding!" signs, and pestered the town until they got the town to put one of those radar "your speed is" devices right in front of their house. This seems like a really stupid tactical error. If you're concerned about the reaction times of drivers endangering your kids, the very last thing you should want to do is to put a flashing sign that demands the driver's attention right in your front yard. Why distract the driver from seeing your kids?