Sorry James and Iamiam,
You may want to read the Wiki definition:
Fuel efficiency in transportation - Wikipedia, the free encyclopedia
There you will find the "passenger miles/gallon" which really doesn't care about any individual load factor but is an intrinsic measure of an airplane's efficiency. How much is stuffed in a plane or car is the uncontrolled variable so for any given car:
- How many jockeys?
- How many NBA players?
- How many undergraduates?
- How many circus clowns?
- How many autopilots?
The load is just another way, a variable way, to bias an efficiency 'claim.' It is not intrinsic to the vehicle but something chosen, a 'special pleadings' and often amusing.
In contrast, the passenger and cargo space is fixed and can be measured for each vehicle. The distance traveled can also be measured. The fuel consumed is also measured. Whether or not one uses all of the payload capacity is not relevant as the vehicle is sold to meet the owner's requirements. It is also why a vehicle too small has difficulty being sold in large numbers.
So last week, my Prius was much more efficient than any Insight because I had a spare door in the rear seat. It took all of the three passenger seat space as I was looking for a shop to install it. So that loading was the equivalent to one driver and three passengers, the rear seat area. Do you agree?
Let me put it this way, I would be happy to carry a large box in the passenger seat and three large boxes in the rear seat. Ok, let's make them inflated beach balls (or inflated mannequins.) With the driver, I now have five seats worth of payload and fully exceed the efficiency of the Insight. Would you agree?
Trying to use the load is called a 'special pleadings' and has nothing to do with the vehicle efficiency:
(output) / (input)
output - passenger and cargo volume miles
input - fuel consumed
NOTE: efficiency could be expanded to include time, another input.
Bob Wilson
ps. I see inflatable display mannequinns on Ebay for $10/each. So for $40 my Prius suddenly becomes more efficient than the Insight. <GRINS>