CHICAGO--(BUSINESS WIRE)--Fitch Ratings has assigned a 'AA-' rating to the Illinois State Toll Highway Authority's (ISTHA, or the authority) $400 million series 2015A toll highway senior revenue bonds. The Rating Outlook is Stable. The rating reflects the essentiality of the tollway system, evidenced by its stable and growing traffic base since 1974 and demonstrated moderate price elasticity. It also reflects prudent debt management, as illustrated by its strong historical and projected debt se