Detroit & Mackinac 975 switches a long line of boxcars onto the Chief Wawatam at Mackinaw City, on February 24, 1981.  The two gondola cars are called "idler" cars.  They are always attached to the heavy engine, and allow the string of cars to be placed into the ship without requiring the heavy locomotive to move onto the moveable dock or ship, for safety reasons.  Below, another photograph of the 975, on April 25, 1978.  [Both, Neil Plagens]

Above, D&M 975 appears to get assistance from D&M GE switcher No. 10.  We are not sure why No. 10 is helping, as it may not have been equipped for multiple unit operation.  January 31, 1978.  [Neil Plagens]  Below, D&M 977, another Alco product, switches the Chief in June, 1979.  [Rob Kitchen].

On the opposite side of the Straits, the Soo Line handles the chores of loading and unloading the Chief, with an EMD GP-30.  Flat cars are used as idlers.  [Rob Kitchens]