Below is a Google Map of the Tappan Zee Bridge and the I-287 corridor

As shown below, the I-287 corridor in New York consists of both the New York State Thruway (owned by the Thruway Authority) and the Cross Westchester Expressway (owned by the New York State Department of Transportation).

Any bridge built within 25 miles of the Tappan Zee Bridge falls under the jurisdiction of the Port Authority of New York and New Jersey.  As shown below, the Tappan Zee Bridge was built just north of that line so that the state of New York would not need to share toll revenues with a bi-state agency.