bridge was not built with a plan that was "conducive to long-term durability” and that the Tappan Zee’s engineers designed it to be “nonredundant,” meaning that one "critical fracture could make the bridge fail completely because its supports couldn’t transfer the structure’s load to other supports." The Metropolitan Transportation Authority (MTA) studied the feasibility of either including a rail line across the new bridge or building the new bridge so a new rail line can be installed at a future date. Commuter rail service west of the bridge in Rockland County is limited, and the MTA studied expansion possibilities in Rockland County that would use the new bridge to connect with Metro-North's Hudson Line on the east side of the bridge along the Hudson River for direct service into Manhattan. On September 26, 2008, New York state officials announced their plan to replace the Tappan Zee Bridge with a new bridge that included commuter-train tracks and lanes for high-speed buses. The bridge was estimated to cost $6.4 billion, while adding bus lanes from Suffern to Port Chester was estimated to cost an additional $2.9 billion. Adding a rail line from the Suffern Metro-North station and across the bridge, connecting with Metro-North’s Hudson Line south of Tarrytown, would have added another $6.7 billion. The plan was reviewed for its environmental impacts. In 2013, the New York State Thruway Authority began building the new Tappan Zee Bridge, a double-span bridge (four lanes per span in opposite directions) with designated bus lanes, to the north of the old bridge. Construction began as scheduled during 2013, with completion projected for 2017. Closure and demolition of old span The northbound/westbound span opened on August 25, 2017. Southbound/eastbound traffic remained on the old span until October 7, 2017, when it was temporarily shifted to the newer northbound/westbound span. The old bridge was subsequently decommissioned. The replacement bridge project was expected to be completed by June 15, 2018 at a cost of $3.98 billion. After some delays, it was announced that the new southbound/eastbound span would open to traffic on September 8, 2018. However, the opening of the new eastbound span was delayed when a piece of the old bridge came loose on September 7 while being demolished. The eastbound span, which was away from the old bridge, remained closed until the old bridge could be stabilized. The old bridge was then demolished in piecemeal fashion in