The Alanson Swing Bridge is currently under repair.  Although I don't have any details regarding the project, the repairs appear to be extensive in scope.  If any readers have more information, please feel free to comment.  Information regarding this interesting attraction is provided below, courtesy of Ferris State University.   

Alanson Swing Bridge

"The Shortest Swing Bridge in the World" is a single lane bridge used for pedestrians, snowmobile, and automobile traffic.  The original bridge built is 1902 was operated by a manual key pinion (about five feet high) on a rack. Today the rebuilt bridge (almost a replica) is operated by hydraulics and still uses a rack and pinion gear system.  The approximate height clearance is 4 ft (a typical 21 ft I/O will clear by less than a foot).  If you need to have the bridge opened, sound your horn three times, and wait (as all other boaters should).  Passage for boaters, is one way.  Plan ahead, keep an eye on traffic, wait your turn. It is easy to navigate the narrows at the bridge, however, be prepared for boats tying up and getting ready to get back boating from mooring docks and boats houses in the area.  Busy days in this area can be quite congested.

Courtesy of Ferris State University, "The Waters of the Inland Route"