Excellent op-ed from an assistant professor of transport engineering at the University of Texas. Read it all. We should share the crap out of this article...

“Current best practices in transportation engineering — supported by extensive research by organizations such as the Federal Highway Administration, the National Cooperative Highway Research Program and the Institute of Transportation Engineers — is that speed limits should be set at the 85th percentile of traffic speed. That is, only about 1 out of 7 cars should be driving faster than the speed limit. Any more than that and the speed limit should be raised.”