New York State Route 400 (NY 400) is a state highway located within Erie County, New York, in the United States. The northwest end is connected to the New York State Thruway (Interstate 90 or I-90) and the southeast end terminates at NY 16 in the town of Aurora. NY 400, a limited-access highway known as the Aurora Expressway, roughly parallels NY 16 between the two locations.