Seasonal Weight Restrictions
One of the most common business interactions with a county road agency concerns seasonal weight restrictions – sometimes called “frost laws.”
While roads are concrete and asphalt and look indestructible, they can actually be quite fragile in late winter as frost comes out of the ground. Even strong late-winter sunlight on the dark paved surface has a significant impact on a road.
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. When trucks and heavy equipment travel over a layer of concrete or asphalt that isn’t well supported beneath, lots of permanent cracks can occur.
Seasonal weight restrictions in effect. Road commissions must strike a balance between “business as usual” and protecting the roads, and most of them employ licensed Professional Engineers (PEs) to make these decisions. Most usually consult neighboring road agencies, as well.
By law, road agencies can enact weight restrictions on any roads not designed as “all season” roads. All season roads are much thicker and designed to allow trucking year around.
Seasonal weight restrictions lower axle-loading limits and reduce maximum travel speeds for certain vehicles. Click here for details about seasonal weight restrictions and their effect on axle loading and speed limits.
Note that some limited classes are exempt from these restrictions after a permit is filed.
For spring weight restriction bulletins from MDOT on the Trunkline System, click here.
For MDOT's information resource for commercial trucking, click here.