WHITE PLAINS, N.Y. — A planning document says a new Tappan Zee Bridge would be built to last more than 100 years.

It also says the bridge would include space that could eventually be used for commuter trains or other mass transit.

The document, from state and federal highway agencies, was posted online in advance of public presentations scheduled for Tuesday and Thursday evenings.

It predicts a 2017 opening.

The existing 56-year-old bridge, spanning the Hudson River in New York City’s suburbs, is overcrowded and deteriorating. A replacement bridge project was boosted earlier this month when President Obama declared it eligible for fast-tracked federal approvals.

The anticipated mass-transit aspects of the new bridge had been dropped to cut costs. But the planning document says a new bridge should not preclude future mass transit.