[dwtaylorpdx]

I worked a project several years ago doing core analysis on LA traffic patterns.

The goal was to determine what the primary cause of traffic stalls were.

After 2 years of analysis and simulation testing despite all the preconceived theories, the major cause of traffic jams and accidents was determined to be cars going 10 miles an hour or more UNDER the speed limit. Cars that were speeding and causing accidents were in excess of 30 miles an hour over the limit and accounted for < 1 in 40 accidents and delays. The split was something like 15% for speeders 55% were slow drivers the rest was mechanical failure or stupidity..

And the 55 magic number is pulled out of thin air. There is nothing magic about 55.
My BMW gets peak mileage at 65 not 55. (34MPG to 36 MPG depending on the terrain.)
Drops to a consistent 30 to 32 mpg at 55. I still get 30 MPG at 75, My state the limit is 65 and I don't save significant time by going to 75 for a < 300 Mile trip so 65 it is...

On the other hand WA lets me go 75 and when its a drive from Portland to Spokane thats 400 Miles and Its all flat, I let the car find its sweet spot and that's usually approaching 75. I tend to exploit the terrain, turnoff the cruise down hill and let it coast up.

Portland to Spokane About 400 miles.
5.3 hours at 75,
6.2 at 65
7.5 at 55

I balance the time against the fuel cost, 45 minutes, not a big deal 2 hours gets my attention, I'm usually working and that travel time is 200 bucks an hour.... vs about 1 gallon of gas. 65 Being the min because I'm not going to lose the time AND the mileage.
I fly when I can but there is a lot of distance between airports in the west and the small towns with no air service.

At the end of the day economics control a lot....

Dave

Side tidbit, the CD of the BMW 318ti is about .34 stock.
The engine is a 1.8 liter with a 5 speed transmission car weighs in at about 2800.