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HOUGHTON COUNTY – Weight restrictions on roads across four counties in the western UP were initiated last week as spring weather patterns brought warmer temperatures to the Copper Country.

Baraga, Houghton, Keweenaw and Ontonagon counties implemented load restrictions on their roads on March 4, while restrictions on all state trunklines in the U.P. started Monday.

Houghton County Road Commission Engineer/Manager Kevin Harju said by law, load restrictions begin March 1.

“The four counties collaborate amongst ourselves and see how the roads are doing,” Harju said. “We compare and take notes on frost depths, road conditions and watching the weather.”

Harju said the road commissioners generally try to announce restriction implementations three days in advance so companies and haulers can have time to move equipment before the restrictions are put in place.

While passenger vehicles are not included in the weight restrictions, Harju said he commonly receives calls from the public regarding privately owned equipment such as tandem-axle or tri-axle trailers.

“A lot of time, we’ll have to go out and look at them,” he said, “because they’ll have a bobcat or a tractor on them, and those are subject to weight restrictions.”

Loads are reduced by 35% on flexible (asphalt) pavements and 25% on rigid (concrete) pavements, and the maximum speed for trucks is limited to 35 mph.

Weight restrictions are designed to reduce damage to road surfaces during spring warming periods.

As frost melts beneath a paved road, the roadbed turns wet and spongy because water is trapped between the pavement and the remaining ice layer beneath, says the County Road Association of Michigan. When trucks and heavy equipment travel over a layer of concrete or asphalt that is not well supported beneath, permanent cracks and pot holes can occur.

“Pavement structure is extremely weak during load restriction periods, because the ground is thawing from the top down,” Harju said. “Water gets trapped between the pavement and the ice layers underneath the roadway, essentially it acts like a water bed.”

Reducing weight loads reduces the flex in the pavement, because when the pavement flexes, Harju said, it creates micro cracks that enlarge and lead to pot holes and further damage.