HOV lane behavior... 4449

No. You take away all speed limits first. (no signs, no enforcement of any type). Then you do a traffic survey to measure speeds people are actually driving, in the total absence of a speed limit. Then you find the speed that 85% of drivers (in the absence of a speed limit) are driving at OR SLOWER. Let's say the actual 85th percentile speed is ~85MPH (very likely in many areas). That would mean that only 15% of drivers would exceed that particular speed under any circumstances (legal or otherwise)

Now the 85th percentile speed is unlikely to be a nice number like 85 or 90. It is more likely to be an in-between like 77 or 82. In that case, round to the nearest 5MPH, preferably in the upward direction.

If you do this, safety will be maximized and loss of property and life will be minimized. Speed doesn't kill, it is speed differences that kill. Also, posted speed limits do not have much of an effect on actual speeds driven, other than the fact that some stupid drivers use an under-posted limit as an excuse to drive in an unsafe manner. (in other words, if the 85th percentile would be 80MPH but the posted limit is 55MPH, it is DANGEROUS to obey the law, as it is creating greater speed differences)

Yeah, someone will argue that the 85th percenters doing 80 in a 55 are the real problem. But the 55MPH speed limit (for example) didn't slow them down, and it never will. You can't slow drivers down by under-posting a road. The best you can do is post it correctly, if you are going to post it at all. It isn't a perfect solution, but there is no perfect solution. If you care about safety, you post limits at the 85th percentile. If you care about maximizing both revenue and carnage, you pull a number out of your butt, such as "55 saves lives". -Dave