Story: Interlockers in Michigan - Updated 12/23/2023

An interlocker was a device at a railroad crossing or junction of two or more railroad lines. An interlocking device controlled the direction, signals, switches, locks and detectors which were within the interlocking limits, and prevented two trains from colliding when crossing through the limits. The majority of interlocking devices were in two-story towers at the crossing or junction. But some were operated from depots, had ground controls for use by train crews, or were remote controlled. Some interlocking devices controlled "half" interlockers which normally had signals on the dominant route, and derails on the other route. Half interlockers were often used for crossings of short spurs or electric railroad crossings.

Compilation

Michigan had 254 interlockers across its 83 counties. A total of 190 interlocking towers existed including 13 which controlled railroad river bridges and the trains which crossed them.

31 Michigan counties had no interlockers.

In the three-county Detroit area:

• Wayne County had 59 interlockers (52 towers). 38 were within what would become the City of Detroit 
• Oakland had 14 interlockers (in 5 towers)
• Macomb county had only one interlocker (operated by a tower in Mt. Clemens)

Other Michigan counties with multiple interlockings (in order by quantity)

• Saginaw County - 19 (2nd  highest in the lower peninsula after Wayne County)
• Kent County - 14
• Marquette County - 11 (the most in the upper peninsula)
• Monroe County - 11
• Bay County - 9
• Calhoun County - 9
• Lenawee County - 9
• Kalamazoo County - 8
• Houghton County - 6
• Ingham County - 6

A handful of interlockers were "ground" interlockers operated by train crews at the crossing. Some were remote controlled by other nearby towers and some were operated from nearby depots. As technology improved, more and more were operated by the dispatcher.

Several interlocking towers were unmanned. An example was M.A.L. crossing in Jackson. After the 1940's, only one GTW train came through round trip each day. The GTW agent/operator at Jackson drove to the tower to let the train cross the MC, and then returned the signals to "proceed" for the Michigan Central.

Today, there are no interlocking towers in operation in Michigan. Interlockers are now remote controlled by railroad dispatchers who are located out-of-state.

To look at individual details of these interlockers, go to the RRHX History section

• Click on "Stations|Locations", then
• Click on the county you wish to look at.
• In each county, there is an "Interlockings in..." page near the top of the list.

Then check the specific locations you wish to read about in the menu.

The interlocking lists do not including all crossings. Many crossings were "stop and proceed" with no interlocked control. Railroad crossings with gates were only included if the gates controlled signals on one or more of the lines.  Also, we have not included many locations which had smaller flagman towers to control only traffic crossing gates. Modern interlockings (known as control points or "CP"s are not included unless they previously had an interlocking tower.

If you know of other locations in Michigan, please let the editor know by filling out the form at the bottom of the page.