Federal Aviation Administration Draft Advisory Circular 150/5360-14A, Access to Airports by Individuals with Disabilities

1.6.5 Designated Public Transportation.
Transportation provided by a public entity (other than public school transportation) by bus, rail, or other conveyances (other than transportation by aircraft or intercity or commuter rail transportation) that provides the general public with general or special service, including charter service, on a regular and continuing basis. (49 CFR § 37.3).