The project timeline originally indicated that the old bridge would be closed in 2016 and that the demolition of the old bridge would begin in February 2017.
The new northbound/westbound span opened on August 26, 2017.
 Southbound/eastbound traffic remained on the existing span until October 6, 2017, when it was shifted to the new northbound/westbound span to allow for the completion of the new southbound/eastbound span.
The northbound/westbound span of the new Tappan Zee Bridge temporarily carried four lanes in both directions until the new southbound/eastbound span was completed.

After some delays, the project was later expected to be completed by June 15, 2018, at a cost of $3.98 billion.
However, the scheduled opening was later pushed back to mid-September.
The new southbound/eastbound span was supposed to open to traffic on September 8, 2018.
An opening ceremony was held on that date, but the traffic shift itself was delayed when a piece of the old bridge came loose on September 7 while being demolished.
The opening of the eastbound span, which was 160 feet (49 m) away from the old bridge, was delayed until the old bridge could be stabilized.
After the old bridge was stabilized, all lanes were opened on September 11, 2018.

Upon completion, the new Tappan Zee Bridge became one of the widest cable-stayed bridges in the world, having a combined width across both decks of 183 feet (56 m).
The new spans equal the width of the relatively short-span, cable-stayed Leonard Zakim Bridge in Boston.
Turkey's 3rd Bosphorus bridge, completed in 2016, has a single deck about 192 feet (59 m) wide.
The bridge is intended to last at least 100 years.

The demolition of the old bridge started in November 2017 with the removal of the first steel section from the Rockland County approach.
The work continued to April 2018 including removal of the truss sections.
In May 2018, the 10-million-pound main span was removed, leaving only the east and west approaches.
The original plan was to complete the remaining demolition by taking down spans piece by piece in order to minimize the environmental impacts.
However, when the instability of the eastern span was discovered in September 2018, it was decided to destroy it outright.
The explosive demolition of the eastern approach took place on January 15, 2019, while the western approach was lowered onto a barge on May 12, 2019 and hauled away.
The project timeline originally indicated that the old bridge would be closed in 2016 and that the demolition of the old bridge would begin in February 2017. The new northbound/westbound span opened on August 26, 2017.  Southbound/eastbound traffic remained on the existing span until October 6, 2017, when it was shifted to the new northbound/westbound span to allow for the completion of the new southbound/eastbound span. The northbound/westbound span of the new Tappan Zee Bridge temporarily carried four lanes in both directions until the new southbound/eastbound span was completed.
After some delays, the project was later expected to be completed by June 15, 2018, at a cost of $3.98 billion. However, the scheduled opening was later pushed back to mid-September. The new southbound/eastbound span was supposed to open to traffic on September 8, 2018. An opening ceremony was held on that date, but the traffic shift itself was delayed when a piece of the old bridge came loose on September 7 while being demolished. The opening of the eastbound span, which was 160 feet (49 m) away from the old bridge, was delayed until the old bridge could be stabilized. After the old bridge was stabilized, all lanes were opened on September 11, 2018.
Upon completion, the new Tappan Zee Bridge became one of the widest cable-stayed bridges in the world, having a combined width across both decks of 183 feet (56 m). The new spans equal the width of the relatively short-span, cable-stayed Leonard Zakim Bridge in Boston. Turkey's 3rd Bosphorus bridge, completed in 2016, has a single deck about 192 feet (59 m) wide. The bridge is intended to last at least 100 years.
The demolition of the old bridge started in November 2017 with the removal of the first steel section from the Rockland County approach. The work continued to April 2018 including removal of the truss sections. In May 2018, the 10-million-pound main span was removed, leaving only the east and west approaches. The original plan was to complete the remaining demolition by taking down spans piece by piece in order to minimize the environmental impacts. However, when the instability of the eastern span was discovered in September 2018, it was decided to destroy it outright. The explosive demolition of the eastern approach took place on January 15, 2019, while the western approach was lowered onto a barge on May 12, 2019 and hauled away.
Tappan Zee Bridge (2017–present)