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Acronyms are common in the world of rigging and heavy transport.  You’ll often hear PST, SPMT. What does the alphabet soup of acronyms mean?  

A PST is a model of a Goldhofer trailer and generally referred to as a self-propelled trailer.  Yes, the acronym and the description don’t match, but as Goldhofer is a German company, perhaps the acronym works in the German language.   

On the other hand, an SPMT is a more generic term and can stand for both self-propelled modular transporter or self-propelled modular trailer. It moves equipment or objects that are too massive or heavy to trucks to transport.

An SPMT is a workhorse of a vehicle composed of a platform supported by computer controlled axles, usually two across and up twelve axles long. The modular nature of the system allows for unlimited configurations by adding axles (or lines) to the length and width of the trailer. On a project site, you’ll often hear it referred to as a 8-line SPMT, 10-line SMPT etc.  

Barnhart uses an SPMT to move a bridge section in California.

Each axle steers independently, which means it can negotiate difficult or uneven terrain and keep the load level. Maneuverability is a big plus. The SPMT can move forward and backward, sideways, diagonally and even make a 360’ turn. It is an invaluable tool when space is limited. 

As for the self-propelled part, movement is provided by a hydraulic power pack which provides power for steering suspension and drive function. A crew member operates the SPMT with a hand-held remote control panel or from a driver cabin.

SPMTs are used in many industries including power and oil, on plant construction sites, and to remove and replace oversize bridge spans on civil projects. This type of trailer is the leader in moving heavy loads.

But because those loads are so hefty, you don’t want to get behind them.  An SPMT isn’t built for speed, moving at no more than five miles an hour.