"Scott en Aztl‡n"
No, it is due to folks who completely disreard the speed limit - which apparently means you. If you think the speed limit is wrong, have it changed. Quit endangering lives by ignoring it and then pleading 85th percentile. I'vs seen all the BS on that subject I can stand. I am not in favor of the 55 mph speed limit. I'd be happy with 70 or 75. I don't beleive the average American is qualified to drive 85 or 90 on heavily traveled roads like I-95. The fact that they think they are qualified does not make it so.
As for the "common speed" of traffic. I am probably driving faster than the average speed of traffic when I am on I-95. I am just not willing to go as fast as the 5 or 10% that seem to be willing to drive as fast as they can till they run up someone else's back. One person doing 85 seems to drag along a whole train. If you knocked out the 10% willing to completely igonore the speed limit, I'll bet the average speed would drop considerably. Without someone to shield them, most of the gross speeders would cower behind people doing 75 in a 70.
Ed