Re:Good luck... (Score 1)

The 85th percentile usually will include peak (read: rush hour) times where speeds are significantly lower than the times where traffic is free flowing. So, the 85th percentile may be a lot lower than you think it would be. The numbers, of course, are a bit biased because everyone is going to drive at a speed approaching the speed limit, hence the 85th percentile will always likely be really close to the speed limit. They would only really change the speed limit if it's a significant increase or decrease over a very long time, given no other external factors. I've heard of some municipalities (city level) even going to a 95th percentile in urban areas.