By Carrie Muehling

ANKENY, Ia. – A recent study funded by the soybean checkoff shows allowing heavier semis to travel the nation’s roadways is not only more efficient, but also safe.

The research looked at expanding semi weight limits on the federal road system from an 80,000 lb. five-axle configuration, which is standard, to a 97,000 lb. six-axle configuration. It considered the impact on motorist safety, wear and tear on infrastructure, and efficiency gains for agriculture and other industries.

While many would assume a heavier semi would be a more dangerous semi, this research shows the contrary is true. Adding an additional axle increases braking friction, so the stopping distance is actually the same.

“The research shows that motorist safety is much stronger related or a function of the number of semis on the road and less a function of the weight of individual semis. So when you allow heavier semis with that additional axle – it’s very key to have that additional axle – you will actually result in fewer miles traveled with semis, which will result in a reduced probability of accidents with fellow motorists,” said Mike Steenhoek, executive director of the Soy Transportation Coalition.

Steenhoek said allowing heavier semis would mean fewer semis could transport the same amount of freight.  With current projections showing an increased demand for semi transportation in the future, that could be helpful.

Steenhoek did acknowledge that bridges are more sensitive to the aggregate weight of the semi regardless of the number of axles. He believes a system allowing heavier semis would have to include a fee or some other funding structure to help maintain bridges.

“For bridges, it’s a different subject. Again, bridges are more sensitive to the weight of the overall semi, so adding axles has less of an impact,” said Steenhoek. “So one of the things that if we were to shift to something like this, we think it would be responsible for those freight interests who would utilize a 97,000 lb. six-axle configuration is to have some kind of fee associated with that and the money from that fee be used for maintaining our bridges, because we would have to have some additional resources for that.”

But overall, Steenhoek said the research shows a transition in this direction makes sense. Many other countries competing with the United States on the international marketplace already allow heavier weights, which can provide real examples of what that system could look like here.

Carrie Muehling can be reached at [email protected].