WisDOT Shows Off SuperLoad Hauler’s Super Cool Self-Propelled Trailers

Superior, WI – A recent social media post by the Wisconsin Department of Transportation (WisDOT) is a great reminder that having the right equipment is paramount to the success of any transportation project.

Over the weekend, WisDOT took to Facebook to show off what has become a standard item of heavy transport equipment across the industry known as self-propelled modular transporters or trailers (SPMTs).


Mammoet, a global leader in heavy transport deploying a fleet of equipment including everything from conventional trailers and barges to skidding systems, moved three super loads through Superior last week using SPMTs.

The heavy loads of oil refining equipment were bound for Husky Refinery in Superior.

The largest of the three loads weighed in at about 394,000 pounds, WisDOT stated.

Two of the SPMTs boasted 18-axle-lines and the third had 12-axle-lines.

Did You Know?

The first modular self-propelled trailers were built in the 1970s.

In the 1980’s though, Mammoet — alongside its partner Schuerle — refined and improved SPMTs.

Some incredible features now offered on SPMTs allow each axle to be individually controlled in order to evenly distribute weight and carefully steer.

Plus, each axle can swivel 270 degrees with some models offering a full 360-degrees of motion.


The control system allows the SPMT to achieve remarkable precision when turning, moving sideways or spinning.

When faced with navigating uneven terrain, some SPMTs allow the axles to telescope independently of each other in order to keep the load flat and the weight evenly distributed.

A hydraulic power pack driven by an internal combustion engine is attached to the SPMT to provide power for drive functions including steering and suspension.

One pack can provide enough power to operate multiple SPMTs, like those delivering to Husky Refinery, or a team of connected SPMTs.

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However, don’t expect to move very quickly when using an SPMT.

They often travel less than one mile per hour.

Some SPMTs are controlled by a worker with a hand-held remote control device while others have a driver cabin.

Semi-trucks are also often used to provide traction and braking for the SPMTs while navigating inclines and descents.


It may look easy, but it’s not.

Extensive route planning, identifying bottlenecks and contingencies, managing interfaces between modes of transport, and handling local transport permits make heavy transport logistical services quite complex.

Coordinating with state and local transportation officials is also extremely important.

In fact, WisDOT said its staff worked for months just to help successfully plan last week’s operation.

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