(5) Intercity transportation. Intercity transportation means intercity passenger transportation or intercity passenger charter service. Intercity transportation does not include transportation provided entirely within a municipality, contiguous municipalities, or within a zone that is adjacent to, and commercially a part of, the municipality or municipalities (within the meaning of section 10526(b)(1) of the Revised Interstate Commerce Act (49 U.S.C. 10526(b)(1)). See 49 CFR part 1048 (regulations defining commercial zones under that statute).