Vertical Lift Highway Spans

The Bronx kills and Harlem river lift spans have much larger deck areas than any previously designed. Some features of their design construction and erection are described below:

Navigation requirements in the Harlem River and the Bronx Kill suggested the need for two vertical-lift bridges over these waterways, as part of Now York City's new Tirborough Bridge. Navigation on the Harlem River is quite heavy, though consisting largely of tugs and barges in tow. Bronx Kill is not now navigable, but a tide lock and ship channel are contemplated through the Kill in the future, connecting the Harlem more directly with the Long Island Sound. High-level bridges at these locations would have been very costly and would have created difficult approach problems both in the Manhattan and Bronx areas. Water traffic does not require high-level bridges at these points, but on the other hand low-level bridges are not possible without imposing great burdens on both water and bridges traffic.