(a) Subject to posted signs and subject to directions by any employee or agent of the authority, no person shall operate a vehicle on the bridge or on its approaches in excess of the following maximum speed limits:

1. (1) 25 miles per hour in or upon the bridge;
2. (2) 15 miles per hour in or upon the approach located within 150 feet north of the toll booth; and
3. (3) 15 miles per hour in or upon the approach located within 475 feet south of the toll booth.