At the north end of Paulsboro, NJ the former PRSL line to Deepwater/Carney's Point crosses over the Mantua Creek on an "A-Frame" movable bridge. These bridges were once common in South Jersey at locations where only a short span was needed to cross a navigable waterway. The bridge span is suspended on one end from the A Frame and pivots on the other, being moved to either position by a cable pulled by a winch. Once the span is in the closed position, the bridge tender locks the span with locking bars, clears the lever operated "smashboard" semaphore signals, and cranks the bridge down onto the north abutment. After the train passes, the sequence is reversed to open the bridge. At the time of the video, the only concession to modernity was an electric motor to operate the winch instead of the old "ship's wheel" cranks which were still available for manual use in case of power failure. You can see them turning on the video as the bridge moves. I was fortunate to catch this sequence as the bridge has been converted to automatic operation and the bridge tender's position and cabin eliminated. Train crews activate the bridge to close by pushing a sequence of tones on their radio.
Bridge was an "A-Frame" design manually-moved (via cranks and wheels) swing bridge of a design used in many other locations in southern New Jersey, particularly along barrier islands of the Jersey Cape. This was the last survivor of the design until its destruction in late 2012.
March 1, 2013: http://www.nj.com/gloucester-county/index.ssf/2013/03/conrai...
Conrail is planning to design and construct a new movable bridge over the Mantua Creek in Paulsboro. This bridge will comply with all applicable U.S. Coast Guard standards and permitting requirements. Construction on a new bridge is expected to begin when the company receives approval from the U.S. Coast Guard and is expected to take until September 2014 to complete. If the existing structure were to be repaired, rather than replaced, it would take the same amount of time.
Lost swing bridge over Mantua Creek on Conrail Shared Assets Operations