B&O Swing Bridge (Philadelphia, Pennsylvania)

 railway, interlocking, railway bridge, swing bridge

The original bridge at this site was opened on July 11, 1886, when freight service began on the Baltimore and Ohio Railroad's extension to Philadelphia (now the CSX Philadelphia Sub). The original bridge was a four-span iron through truss bridge with a center swing span for the passage of river traffic. The B&O replaced it with the current bridge, a three-span through truss bridge with center swing span, in 1910. The rebuilding was done by the American Bridge Company. During the process, a tugboat passing the bridge grounded on the riverbank and had to be freed by a B&O locomotive. The bridge was struck by the tugboat Radnor, hauling a barge loaded with oleum, on March 12, 1924.

The bridge was originally protected by a mechanical interlocking, which was revised in 1914. It was replaced in 1946 with an electrical interlocking, which also controlled the nearby junction with the Reading Company at Eastwick.

In 1977, the Chessie System, then owner of the bridge, did engineering studies of the swing bridge mechanisms, and determined that extensive rehabilitation was needed. However, the project was placed on hold for decades, and, despite associated FRA violations and operational difficulties, was not revived by successor CSX Transportation until late 2003. Completion was planned for May, 2004. There were issues with rail traffic, controlled by CSX, and river traffic, with the US Coast Guard concerned with the fact that during construction the bridge cannot be opened.

The rehabilitation was completed on time in May 2004, including extensive work on the miter rails, which are mechanisms allowing for disconnecting the steel rails when the bridge is opened, and reconnecting the rails when the bridge is returned to rail traffic.