Answer:

mainline

AnswerCrossword Clue
MAINLINEPrincipal route of a railroad
MAINLINETrack for the Century.
MAINLINEPart of a railroad.
MAINLINEPosh Philadelphia suburban area
MAINLINEPosh area of Phila.
MAINLINEPrincipal highway
MAINLINEChief artery
MAINLINESuburban Philadelphia area
MAINLINEIt's not the road less traveled