Possible Clues:

• E-ZPass site: Abbr.
• I-90 in Mass., e.g.
• It may be associated with an 'I': Abbr.
• Place for booths: Abbr.
• Map abbreviation
• Tollway: Abbr.
• Rte. with tolls
• Rd. often spanning an entire state
• Pay rd.
• Plaza locale: Abbr.