80 MPH = Less than 40 MPG on the highway

I think self-driving cars, abiding by the speed limits, can't happen too soon.

 

Totally agree. But just watch how the speed racers will all complain about "big brother" taking control of their lives.

I would have no problem with an 80mph speed limit if all cars are on "autopilot" and going the same speed at a safe following distance. I drive a PIP with the radar cruise control which helps in traffic, but it is not autopilot. I have a Tesla model 3 on order. It appears that they will come with autopilot as an option. Apparently there has been some problems with Tesla's autopilot feature and that doesn't surprise me. Most Tesla autopilot accidents have been caused by drivers watching a movie, or even snoozing while in heavy traffic. Tesla's autopilot does require constant monitoring and eyes-on control even though the driver's hands may be off the steering wheel. It will be a couple of years before my Tesla 3 is delivered.

Because someone made themselves "late for work" does not mean they should endanger my and my family's lives by driving unsafely.

 

Just got back from a trip across WY and MT. The 26th, 28th and 29th were done with cruise set at an indicated 80 mph, air set at 68, stereo blasting and my XXL American nice person in the driver seat and a couple of bags in the back. 29th was some tight mountain road driving, some zipping around a MT city, some very short runs on the interstate going from 0 to 80 back to 0 again in less than 5 miles, things like that.

The 29th I was fighting some pretty strong winds in WY again.

 

Don't forget that drag increases by the square of the speed, I believe.

 

Correct, as far as aerodynamic drag force, which predominates at high speeds. That means the power required to overcome that drag force increases with the cube of the speed.

Rolling resistance (aka tire drag) is almost (not exactly) independent of speed.

 

Should we clarify that we're talking air speed, not ground speed?

Pilots have a drag curve of their aircraft that plots induced drag and parasitic drag (made up of form drag, the shape of your plane, and skin drag, how rough your plane is). At low air speed the wing needs a steeper angle of attack to maintain altitude, this creates more induced drag. As air speed increases the wing creates more lift so you lower the angle of attack. This reduces induced drag, but the higher air speed increases parasitic drag. If you plot both of these with total drag on the y axis and air speed on the x axis you get a U shaped curve. You want to fly in the bottom of the U to maximize endurance (basically MPG). I've always thought it'd be interesting to fit a car with a pitot tube and set cruise on the open road to an air speed rather than a ground speed. Air speed info would also be useful for finding drafting opportunities.

 

Thanks for that more detailed information. So much better than mine, but unless you drive through a vacuum you're gonna find the aerodynamic drag is exactly the same whether you're in a fighter jet or a Prius.

 

I thought there was a difference too, something to do with the closeness to the ground causing additional restriction to progress. It was decades ago I read about air below the car causing eddies or pressure or something - could the road surface be a factor?

 

According to the scangage pushing 80 mph it reads under 40 mpg going up a incline at 80 mph reads 12-17 mpg your pushing engine rpm 3200-4,800 rpm. our TDI golf read out 32.5 mpg at 110 mph.

 

I'm ready to believe that with the reservation that they are just snapshots of what's possible but don't real really reflect real life averages. Thanks for uploading your data though. It's impressive!