The faster interstate daily drivers are already doing 85 mph in Ohio.
I sometimes do so as well.
As was noted above, drivers proceed at a speed comfortable for them in the vehicle they're driving.
Those who want to go slower are free to do so, although they should keep to the right.
A real problem in this country is those who feel that they can change lanes directly in front of much faster traffic, as well as those who clog the left lanes of fast moving interstates.
I drove the old BMW four hundred miles today, at just under 3500 revs in fifth, which equates to just under 75 mph.
I stayed out of the way of faster traffic, speeded up to pass long lines of trucks, and got 32.5 mpg on this tank.
Had I gone 80 mph or so, I would have likely gotten ~30.5 mpg.
The point is that the speed limit was irrelevant to me and everyone else.
Everyone drove as they pleased, and there were no problems as long as everyone moved to the right to let the faster traffic go past, or speeded up to pass the slower traffic.
Speed doesn't kill.
Drunk and inattentive driving kill.