"Texans brush aside such concerns as fuel efficiency or the cost of gasoline. Engineers calculate that drivers burn 7% more gas per mile for every 5-mph increase in speed above 60 mph. Texans calculate that their Hummers need bigger gas tanks...
...85% of drivers on the two segments of I-10 and I-20 were averaging 80 mph, 5 mph above the current 75-mph speed limit, so officials reasoned that raising the limit would simply be a bow to reality.
The assumption is that a majority of drivers, if left to their own speedometers, will collectively achieve a safe operating speed, and that speed should be the primary factor in setting the legal limit.
This is not, however, a particularly popular notion among traffic safety experts."