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joe dog. Device with a dead axle that converts a single-axle tractor to a tandem-axle tractor. It hooks over the tractor's fifth wheel, replacing it with another for the semi to be hooked onto.reference 1

This is a specialized term exclusive to the drayage industry. The origins are unclear.  It may be that this dog is a considered a kind of latch.  Or it maybe that the joe dog acts as a kind of leash in pulling the second trailer behind.

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 figure 2

Elusive as the origins are, it seems likely that the use of joe dogs led to double-bottoms or tandem trailers being referred to as “a set of pups.”



1. Industry Terms. 2002. Markel Professional Transport Training. Accessed May 2 2003 from http:// www. industry-i-q.html .



About the illustrations: Figure 1 shows a classic single axle joe dog. Figure 2 shows how the joe dog (in this case, one with two axles) is employed. Illustrations by the author. Last updated: July 28, 2009
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