I worked on avionics equipment. That did not make me into a commercial pilot, but one becomes somewhat oriented to the science involved. When a commercial pilot makes a flight plan (I assume these days it is done via laptop) he has to find an altitude and the optimum winds for best great circle time traded off with fuel efficiency. A large plane takes a great amount of fuel, and fuel costs are of prime importance for airline profitability. So, one flies at the altitude and speed which will give optimum efficiency, compatible with landing slots at the destination.
One of my favorite tales was told by a man who has lived in Muslim nations. He said the first time he left Dubai for NYC, the plane actually went east for a while. Apparently, this is to avoid certain unpleasant folks who like to fire rockets at aircraft. Then, they turned and took a great circle over the Pole to NYC.
One of the avionics company’s produced cockpit controls for TRAINS based on airplane cockpit controls. Every inch of rail is digitalized and the train computer even tells the engineer what speed to go when going up a hill, based on the weight of the consist (entire train.) For maximum fuel efficiency.
Everything is reported to the maintenance headquarters, including the equivalent of OBDII, as far as bearing wear and other stuff.
If the engineer is under the influence of… the central office can tell because he may not be heeding the instructions of his cockpit computer. And, they allegedly can over-ride the controls and bring the train to a halt if something scary is happening in the cabin of the locomotive. For example, someone told me the headquarters might pop a message on the cabin display unit telling the engineer to enter a certain number and if he does not respond within a certain time, it would indicate his performance is impaired. And, if they cannot communicate by radio, this would be grounds to shut it down.
Source: I once wrote an article on this for one of our company’s employees newsletters.
Cars and trucks are a trade-off between engine and transmission design. If you spent too much time accelerating slowly, with the transmission not locked in a higher ratio, or overdrive, you lose efficiency. If you accelerate too fast, you burn too much gas overcoming inertia. Tom and Ray have said the highest efficiency would be when your car locks the transmission in overdrive, no faster, unless there are hills to compensate for.
My 2002 Sienna gets 24 mpg at 70 mph. At 65 mph, it goes up to 26 mpg.
There is a state in Mexico, a very nice, high velocity divided tollway, but speed limit for the entire state is 80 kph, less than 50 mph. I have not been able to calculate my gas mileage because it doesn’t use enough to calculate. I wouldn’t be surprised if that low speed it doesn’t approach 30 mpg or more.