Humans driving faster than is safe, even if due to emotions, is still human error. The primary limiting factor on safe speeds (at least on "proper" highways) are humans and their poor reaction times.
Couldn't be said enough. What's sad about people that speed too, is that they mistakenly believe that they are the only ones affected by their speed. When in fact most of the affected people are the ones that feel safe pulling into an left-turn intersection knowing the speed limit is 25 and realize too late that someone is barreling toward them at 45. I wish there was more statistics about this phenomenon, but I wholeheartedly believe the mistake speeders make is thinking they have complete control and, yes while they may be good drivers in a certain aspect - the ignoring of commonly known road speeds is why they are, in fact, not good drivers.
