Michigan Oversize and Overweight Trucking Permits

Operating oversize or overweight loads in Michigan requires strict adherence to the regulations set by the Michigan Department of Transportation (MDOT) and the Michigan Vehicle Code. Unlike many other states, Michigan utilizes a unique 'Michigan Legal' weight formula based on axle spacing and the number of axles, rather than just the federal bridge formula. Carriers must obtain permits for any vehicle exceeding 8 feet 6 inches in width, 13 feet 6 inches in height, or 75 feet in length for most combinations. For weight, any vehicle exceeding the statutory limits—typically 80,000 pounds gross vehicle weight or specific axle maximums—must secure a single-trip or annual permit before entering the state highway system. DispatchTool assists carriers in managing these complex requirements by providing truck-safe routing that accounts for Michigan's numerous weight-restricted bridges and low-clearance structures. The platform allows dispatchers to store permit documentation and weight tickets directly within the load file, ensuring drivers have digital access to required MDOT authorizations during roadside inspections. By integrating state-specific permit data into the dispatch workflow, fleet managers can better estimate toll and permit costs before booking a load. Create a DispatchTool account to start organizing your Michigan permit documentation and routing today.

Standard Legal Dimensions and Weight Limits

In Michigan, the maximum legal width for any vehicle is 8 feet 6 inches, and the maximum legal height is 13 feet 6 inches. For length, a semi-trailer cannot exceed 53 feet, and the overall length of a tractor-trailer combination is generally limited to 75 feet on designated highways. Michigan's weight laws are distinct; the maximum allowable gross vehicle weight can reach up to 164,000 pounds on 11 axles, provided the weight per axle does not exceed 13,000 pounds for axles spaced 9 feet or more apart. If a load exceeds these 'Michigan Legal' standards, an overweight permit is required. Carriers must be aware that during 'Spring Weight Restrictions' (Frost Laws), many non-interstate roads see allowable axle weights reduced by 25% to 35% to protect the pavement from damage.

MDOT Permit Types and Fee Structure

MDOT offers several permit types based on the duration and frequency of the move. A Single Trip Permit is valid for 5 days and typically costs $15 for oversize-only loads or $50 for overweight loads. For carriers moving frequent loads, an Annual Permit is available at a cost of approximately $100 for oversize and $200 for overweight, depending on the specific dimensions and gross weight requested. Special 'Supermove' permits are required for loads exceeding 16 feet in width, 15 feet in height, or 150 feet in length. These moves require a more intensive review process and may incur additional engineering fees if a bridge analysis is necessary to ensure the infrastructure can support the extreme weight.

Escort and Pilot Car Requirements

Pilot cars, or escort vehicles, are mandatory in Michigan when a load exceeds specific size thresholds to ensure the safety of the traveling public. For loads over 12 feet wide but less than 14 feet wide, one rear escort is required on multi-lane highways and one front escort on two-lane roads. If the width exceeds 14 feet, two escorts (front and rear) are mandatory. Any load exceeding 15 feet in height requires a front escort equipped with a high-clearance pole to check for overhead obstructions. Escort vehicles must be passenger cars or pickup trucks with a minimum of 4 wheels and must be equipped with amber flashing lights and 'Oversize Load' signs measuring at least 5 feet long and 12 inches high.

Seasonal Weight Restrictions (Frost Laws)

The Michigan Department of Transportation and local County Road Commissions enforce seasonal weight restrictions every spring, typically between February and May, depending on the weather. During this period, axle loading is reduced to 'Normal' or 'Restricted' levels. On 'Restricted' roads, the maximum axle load is reduced by 35% and the speed limit for trucks is reduced to 35 MPH. Michigan state trunklines are categorized as Green (no seasonal restrictions), Gold (seasonal restrictions apply), or Black (seasonal restrictions always apply). Drivers must check the MDOT 'Restricted Map' daily during the spring season, as permits for overweight loads are generally not issued for travel on restricted routes during the thaw.

Travel Time and Holiday Restrictions

Oversize loads in Michigan are generally restricted to daylight hours, defined as one-half hour before sunrise to one-half hour after sunset. Movement is permitted on Saturdays until 3:00 PM for loads not exceeding 10 feet wide, 14 feet high, or 90 feet long. Sunday travel is strictly prohibited for all permitted loads. Furthermore, movement is disallowed on major holidays including New Year's Day, Memorial Day, Independence Day, Labor Day, Thanksgiving, and Christmas. If a holiday falls on a weekend, the restriction usually extends to the Friday before or the Monday after. Specific metropolitan areas like Detroit, Grand Rapids, and Flint may have additional peak-hour curfews (typically 7:00–9:00 AM and 3:00–6:00 PM) for loads exceeding 12 feet in width.

Mobile Home and Special Equipment Rules

Michigan has specific regulations for the movement of mobile homes and modular units. These loads are permitted up to 16 feet in width at the base and 18 feet at the eaves. They are subject to the same escort requirements as other oversize loads, but they must also adhere to specific towing speed limits, often capped at 45 MPH or 50 MPH depending on the width of the unit. For heavy equipment such as excavators or cranes, the boom or bucket must be retracted and secured to minimize the dimensions. If the equipment is being moved on a trailer, the overall height must be measured from the ground to the highest point to ensure it stays within the permitted 13' 6" or the specific height granted on the MDOT permit.

Sources

Michigan Department of Transportation (MDOT) (2024) — https://www.michigan.gov/mdot/business/permits/oversize-overweight-permits Michigan Legislature - Michigan Vehicle Code Section 257.722 (2024) — http://www.legislature.mi.gov/(S(0w4j4r45x4j4r45x4j4r45x))/mileg.aspx?page=getObject&objectName=mcl-257-722 American Transportation Research Institute (ATRI) Michigan State Laws (2023) — https://atri-online.org/

Frequently asked

What is the maximum weight for a truck in Michigan without a permit?

The federal limit is 80,000 lbs, but Michigan allows up to 164,000 lbs on 11 axles without a permit, provided the weight is distributed according to the Michigan Legal formula of 13,000 lbs per axle.

How much does a single trip oversize permit cost in Michigan?

A standard single-trip permit for an oversize load (up to 12 feet wide) costs $15 and is valid for 5 days of travel.

Are escort vehicles required for a 12-foot wide load in Michigan?

Yes, one escort is typically required for loads over 12 feet wide. On two-lane roads, the escort must be in the front; on multi-lane highways, the escort must be in the rear.

Can I travel at night with an oversize permit in Michigan?

No, Michigan generally restricts oversize travel to daylight hours only. Movement is prohibited from 30 minutes after sunset to 30 minutes before sunrise.

What are the Michigan Frost Laws?

These are seasonal weight restrictions that reduce allowable axle weights by 25% to 35% on certain roads during the spring thaw to prevent pavement damage.