Quote Originally Posted by LD71 View Post
...my own experience shows a saving in consumption...Therefore my observation is that lower speeds = higher mpg.
I agree: driving slower uses less fuel (with some notable exceptions, such as higher-performance vehicles geared for higher speeds). However, the issue is not whether driving 55 saves fuel versus 65 - we can agree that it does - the issue is whether a 55 mile per hour speed limit saves fuel versus a 65 mph speed limit.

The answer is: it doesn't.

Why not? Because people don't drive at artificially-low-set speed limits, especially 55 (or even 60 or 65) mph on an interstate-quality highway.

Take a look at this chart:
http://www.eia.doe.gov/emeu/aer/txt/ptb0208.html

Note the "miles per gallon" columns. Note that it gradually dropped from 1949 to the late 70's, when CAFE was initially implemented (initially 1975, phased up standards to 1990). From there it gradually increased to 1990-91 when the last levels of CAFE were implemented. Notice ZERO change (actually, an increase in fuel economy) when the NHMSL was repealed in 1995.

While driving 55 mph will save fuel when compared to driving 65 mph, the 55 miles per hour speed limit had ZERO effect on fuel consumption simply because people ignored it wholesale. And, no amount of enforcement binges, tax rebates to the states, and mass-market media campaigns to the contrary changed that.

The majority of people will drive at a speed that is safe for the conditions; on interstate-quality highways that speed is well above 55 mph. Mandating the speed limit to 55 mph will have negligible affect on the speed people drive, proven by the "success" of that speed limit during the Great Experiment. Since people are not driving at 55 mph, there will be negligible affect on actual fuel consumption. Since the stated reason for dropping the speed limit to 55 is to slow people down to save fuel, and it has been proven time and again to not work, setting the speed limit at this artificially-low speed will have no affect on the amount of fuel used.

Ergo, why make criminals out of people with no positive effect(s)? You would have just as much chance getting people to drive 55 now within the existing speed limits (which is perfectly legal to do) as you would trying to get people to drive 55 with a 55 mph speed limit.

In other words: zero.

Greg