Half of the $4-billion Tappan Zee Bridge replacement, named for the late Gov. Mario Cuomo (D), opened to traffic on Aug. 24. Rockland County-bound traffic can use four lanes of the 3.1-mile cable-stayed span, while design-builders Tappan Zee Constructors continue work on its Westchester County-bound twin. Demolition of the old bridge’s landings is set for fall.