When it opened in 1931, the Bayonne Bridge — with its parabolic arch connecting Staten Island and Bayonne, N.J. — was an engineering marvel, boasting the longest unsupported span of any steel arch bridge in the world. But the height of its roadway, at 151 feet above the Kill Van Kull waterway, is increasingly insufficient for the large container ships now calling at the container ports of Staten Island and New Jersey.

To ensure continued access for these ships, and for the even bigger ones likely to arrive after the opening of an expanded Panama Canal next year, the Port Authority of New York and New Jersey is undertaking a $1.3 billion project to raise the roadway of the bridge by 64 feet, to a height of 215 feet above the water. While the project itself is all but unprecedented in bridge engineering, the trickiest part lies in completing the construction while the bridge remains open to traffic.