> My understanding is that speed limits are set by measuring the speed people are driving on the road and then determining a speed at which roughly 15% of the d

> My understanding is that speed limits are set by measuring the speed people are driving on the road and then determining a speed at which roughly 15% of the drivers are exceeding that limit. That is not how all speed limits are set; it just one possible technique: https://safety.fhwa.dot.gov/speedmgt/ref_mats/fhwasa12004/ https://safety.fhwa.dot.gov/speedmgt/ref_mats/fhwasa12004/