(see image half way down on the right) http://geographylaunchpad.weebly.com/the-friction-of-distanc...
[1] http://anna.ps/blog/train-times-v-house-prices-graphing-the-...
A passenger car and a long-haul airliner are about equivalently efficient, on a fuel-per-passenger-mile basis (assuming a high load factor for the aircraft, and a single occupant for the auto).
Rail is far more efficient, and time-competitive with air for modest to fair long trips (given high-speed rail).
Shipping is the most efficient form of transport by far, but also one of the slowest.
Automobiles require roads of some description, though they can flexibly shift routes across these. Aircraft and ships require ports, though have freedom of movement exclusive of these (with some choke-points: straights and canals, mostly, for ships).
Rail is almost the equivalent of "ships on land", though the right-of-way itself is required. The requirements for these are comparatively modest for basic service, though high-speed and high-capacity routes, and switching, increase requirements.
It's an interesting field.
http://www.slate.com/articles/business/the_juice/2014/07/dri...
The actual efficiencies depend tremendously on the range of the trip, the loading of the aircraft (or car), and base vehicle efficiency.
But ~30 - 40 passenger miles/gallon are possible in either.
For cargo, the (again, very rough) numbers are:
Ship: 514 ton * mile / gallon
Rail: 202 ton * mile / gallon
Truck: 59 ton * mile / gallon
Air: 13 ton * mile / gallon
Something I had cause to look up the other day as I was trying to figure out how to ship my M-1 Main Battle Tank.
https://plus.google.com/104092656004159577193/posts/MZ5Pi7AT...