@Dtrrman....Rocko is correct about the number of interlocking towers remaining.
As the Senior Operator [[15 years now) in the Short Cut Tower, we averaged 100+ train movements PER DAY [[over 36,500 yearly total) on our territory last year, as well as 1,560 bridge openings [[yearly total). We have a Union Switch and Signal Type "F" interlocking machine up here [[same as NS Bridge) and we use it day in and day out, 24 hours/365 days.
I might add that the control of FN interlocking is still technically controlled by a working tower. It is under the authority of the NS Dispatcher, but is actually controlled from the Conrail Bridge.
The Short Cut Tower controls the former DT&I mainline. At the time of its construction in 1922, the DT&I was owned by Henry Ford and the tower was built to be both functional and aesthetically pleasing. The counterweight is in a pit and not visible and the tower is tan brick with a red terra cotta tile roof. The interlocking machine was a top of the line electric interlocking [[keep in mind the Ford/Edison connection) The bridge and tower were the reason that Henry Ford bought the DT&I. The construction of a new bridge over the newly constructed Short Cut Canal would have bankrupted the DT&I and they appealed to Henry Ford for a loan. He decided that with their North-South route from Detroit to Ironton, OH and its interchange with the major East-West railroads and its proximity to the coal fields in Southern Ohio that it would be a good investment and he bought it. He later built the D&I Subdivision which are the tracks leading to the Rouge Plant with the famous concrete arches.
I have attached a photo of the Short Cut Tower and Bridge that I took from the S/S Kaye E. Barker a few years ago.
Attachment 8569