Two years after a fire, the bridge's $81-million rehabilitation project is nearly complete.

The replacement for the Tappan Zee Bridge is hurtling towards completion, with one of its two spans already carrying traffic and the dismantling of the old bridge under way. But with questions over the final cost and the completion date still unresolved, some are asking if N.Y. Gov. Andrew Cuomo has promised too much.

A contractor’s risk of being assessed liquidated damages for delayed performance looms large on any public or private contract.