I'm listening to a radio commercial about the shuttle bus to Newark Airport. They want to claim 184 passenger miles per gallon. My minivan is not particularly fuel efficient, getting about 22-23 miles per gallon (note the missing "passenger" qualifier). On short trips around town, like a run out to Home Depot, I'm the only one in the car and that becomes 22 passenger miles per gallon.
But as soon as the whole family of 4 piles in for a trip to the grandparents, I'm getting 88+ passenger mpg. Still not so good compared to that bus. But I can comfortably seat 7, and have for field trips with the Boy Scouts, at which point I'm up to 154 passenger mpg. Not so shabby now!
The point of my rant here is that we hear or read misleading numbers all the time. There's really nothing wrong with the shuttle bus claim, but most of us hear "184 miles per gallon" and miss that little qualifier "passenger." Changing that one word means a lot. The Apollo spacecraft has the world's best safety record when calculated per passenger mile.