A Study in O.W.L.S.


I love the acronym O.W.L.S., which stands for one way low speed diamond frogs. It is not some type of bird.

These are the O.W.L.S. in Durand, Michigan, at the crossing of two Canadian National lines. The double track belongs to the Flint Subdivision while the single track is the Holly Sub.

With an O.W.L.S. diamond the trains on the high-traffic line cross at a level crossing in a tread bearing mode.

But trains on the lightly-used line must slow to or below 10 mph because its wheels must cross over the flangeway gap for the high-traffic line in flange-bearing mode. There is no flangeway gap for the low-traffic line.

Although these tracks are owned by CN, another user of the Holly Sub at this diamond is the Great Lakes Central.

The advantage of an O.W.L.S. is that trains on the high-traffic line can cross another rail line without a speed restriction. There is less chance of a wheel jumping the flangeway gaps as there is with a conventional crossing.

But from a railroad management standpoint a primary advantage of an O.W.L.S. is less maintenance costs. Now that is something that would make an accountant smile.

Article and Photograph by Craig Sanders


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