The United Arab Emirates at 310 seems like an outlier but if you search for areb drift on youtube you can get a hang of what is really going on.
I live in Brasil, which, unsurprisingly ranks pretty high as well. Bad roads and unsafe vehicles explain part of the problem; but what I think accounts for the gist of it is something I haven't seen commented here: people speed because they want to be faster than other people. The speed limit merely makes this easier by limiting risk averse or society minded people.
I stoped driving long distances a year ago because it was stressing me out and because a car here is too expensive (compared to bus for long distances and taxi for short ones).
What I noticed in myself and in drivers around me was that traffic was regarded as a competition. Being faster was better. If someone was faster than you you'd be passive-aggressive towards him/her (mostly him). Brasil ranks 2nd (to last) on this list because of the way we view cars: they are really expensive, even in an expensive country such as ours. They are regarded as a life milestone, one of the main goal in our lives. They become a way of posing yourself as superior to the masses. This results in a more competitive traffic. Closing people off, tailgating and speeding (50% more than the limit - above this you risk losing your license and get fined for about $500) are the bread and butter of a good sum of our drivers. Our national speed limit is 120kmph (75mph).
Why do most people speed slightly? Is it because of the time they will save? I bet most don't even look at their watches while doing so. For a fixed distance, the speed x time is a hyperbole, which means diminishing returns for greater speeds for distances greater than the value of your speed. I posit that the gain is not time, but a better position at an acceptable risk in a competitive game we call transit.