This web site has a great list of all mechanical modes of transport and their passenger miles per gallon (number of passengers the vehicle can hold multiplied by its MPG. For example a 20 MPG car that can hold 4 would be 80 passenger MPG).
The most efficient are trains. They get great passenger miles per gallon because they can hold a lot of passengers and consume relatively small amounts of gas. For example your typical subway gets the equivalent of 2,500 passenger MPG!
The least efficient are boats, planes and sports cars. The concord for example gets 15 passenger MPG….
Cars are somewhere in between.
The moral of the story is that public transportation is better than cars, more specifically land based public transport.
If you are green minded in Brooklyn this is an easy goal to meet since it is easy to take the subway. Or the bike, which is not listed on the web site since a bike gets unlimited miles per gallon (of gasoline at least).
As a New York green contractor sometimes people look at us funny when we show up by bicycle instead of a fancy pickup truck. But its all about the MPG baby.