Interesting. Here we use the 85th percentile limit to set speed limits. Every few years the city does a speed study. By law (I think) they are supposed to set the limit at the speed 85% of drivers are at or under. If they don't, they're supposed to provide a justification for deviating from the rule. The idea is that people naturally drive at whatever speed they feel comfortable driving, instead of fighting it, we cut off the top 15% of speeders and set the limit there to minimize speed differential which is a big cause of crashes. We use yellow advisory plates when trucks need to slow down for a sharp curve or something.

That's all theory. In practice we have 5 patrol deputies at any point for the entire county and I rarely ever see city cops. No one has respect for the law. Right of way and speed limits are determined by your bravado, risk tolerance, and your full-sized pickup of choice (provided you make the requisite exhaust modifications to spew thick black clouds of freedom every time you tap the throttle). We call them accidents, but crashes are frequently the result of people not exercising due care when driving. The city keeps building 6 lane 45mph roads with 11-12 foot lanes that make people want to drive 60. I hope the next generation of traffic engineers do a better job of segregating fast roads and slow streets.