Possible Clues:

• Org. that keeps New Yorkers on track
• L.A. bus-and-rail overseer
• Commuter-train org. in many cities
• Letters seen all around New York City
• N.Y.C. travel letters
• Where Charlie was trapped, in a Kingston Trio hit
• Urban transit letters
• 1959 hit with the lyric 'Did he ever return? No, he never returned'
• 1959 hit with the line "Fight the fare increase!"
• Subway co. in a 1959 song