ie transporation to which the public has access (trains, busses, airplaines), as opposed to private transportation (private cars or jets).

I understand the dilemma, as "public transportation" would indicate only public buses or commuter trains etc., so this is my compromise.

Read the links and examples below to see if you get a better idea! =)

"Public transportation," at least in US usage, normally refers to URBAN public transportation, i.e. local buses, trains and boats, not to long-distance transportation. The technical term for what is meant here is "common carrier" (an entity offering transportation as a service to the public, and which is in principle required to provide transportation to anyone who buys a ticket and follows the carrier's applicable rules).