How many gallons of gas per what?

As tigira and I drive to and from work, I sometimes spy a Toyota Prius hybrid with a bumper sticker saying something about how the driver is promoting a more independent America because he's getting 40 miles to the gallon of fuel.

( Looking at the aggregate numbers for groups )

Thus, if there's a city of people who need to get from home to work, yet want to use as little gas overall as possible in doing so, then car pooling is a far more effective than replacing the existing cars with marginally more efficient cars. ( caveats )

An added bonus is that I ponder these thoughts as I zip by the Prius, who is caught in traffic, because I am in the car pool lane and able to continue on at highway speeds.