Mich. Comp. Laws § 257.722 — MI Code / Chapter 257 / Act Act-300-of-1949 / Section 257.722
Maximum axle load; normal loading maximum; designating highways as adequate for heavier loading; restrictions as to tandem axle assemblies; exceptions; public utility vehicles; normal size of tires; maximum wheel load; reduction of maximum axle load on concrete pavements during March, April, and May; exemptions; suspension of restrictions; determination of gross vehicle weight and axle weights; designation of highways for operation of certain vehicles; increase in axle loading maximums; engine fueled by compressed or liquefied natural gas; electric batteries; definitions.
Status: in_force

Sec. 722.

(1) Except as otherwise provided in this section, the maximum axle load must not exceed the number of pounds designated in the following provisions that prescribe the distance between axles:

(a) If the axle spacing is 9 feet or more between axles, the maximum axle load must not exceed 18,000 pounds for vehicles equipped with high pressure pneumatic or balloon tires.

(b) If the axle spacing is less than 9 feet between 2 axles but more than 3-1/2 feet, the maximum axle load must not exceed 13,000 pounds for high pressure pneumatic or balloon tires.

(c) If the axles are spaced less than 3-1/2 feet apart, the maximum axle load must not exceed 9,000 pounds per axle.

(d) Subdivisions (a), (b), and (c) shall be known as the normal loading maximum.

(2) When normal loading is in effect, the state transportation department, or a local authority with respect to highways under its jurisdiction, may designate certain highways, or sections of those highways, where bridges and road surfaces are adequate for heavier loading, and revise a designation as needed, on which the maximum tandem axle assembly loading must not exceed 16,000 pounds for any axle of the assembly, if there is no other axle within 9 feet of any axle of the assembly.

(3) A combination of vehicles may operate on designated highways with not more than 1 tandem axle assembly having a gross weight of 16,000 pounds per axle, if there is no other axle within 9 feet of the assembly. On a combination of truck tractor and semitrailer having not more than 5 axles, 2 consecutive tandem axle assemblies may operate on designated highways at a gross permissible weight of 16,000 pounds per axle, if there is no other axle within 9 feet of any axle of either assembly.

(4) Notwithstanding subsection (3), on a combination of truck tractor and semitrailer having not more than 5 axles, 2 consecutive sets of tandem axles may carry a gross permissible weight of not to exceed 17,000 pounds on any axle of the tandem axles if there is no other axle within 9 feet of any axle of the tandem axles and if the first and last axles of the consecutive sets of tandem axles are not less than 36 feet apart and the gross vehicle weight does not exceed 80,000 pounds to pick up and deliver agricultural commodities between the national truck network or special designated highways and any other highway. This subsection is not subject to the maximum axle loads of subsections (1), (2), and (3). For purposes of this subsection, a "tandem axle" means 2 axles spaced more than 40 inches but not more than 96 inches apart or 2 axles spaced more than 3-1/2 feet but less than 9 feet apart. This subsection does not apply during that period when reduced maximum loads are in effect under subsection (8).

(5) The seasonal reductions described under subsection (8) to the loading maximums and gross vehicle weight requirement of subsection (12) do not apply to a person hauling agricultural commodities if the person who picks up or delivers the agricultural commodity either from a farm or to a farm notifies the county road commission for roads under its authority not less than 48 hours before the pickup or delivery of the time and location of the pickup or delivery. The county road commission shall issue a permit to the person and charge a fee that does not exceed the administrative costs incurred. The permit must contain all of the following:

(a) The designated route or routes of travel for the load.

(b) The date and time period requested by the person who picks up or delivers the agricultural commodities during which the load may be delivered or picked up.

(c) A maximum speed limit of travel, if necessary.

(d) Any other specific conditions agreed to between the parties.

(6) The seasonal reductions described under subsection (8) to the loading maximums and gross vehicle weight requirements of subsection (12) do not apply to public utility vehicles under the following circumstances:

(a) For emergency public utility work on restricted roads, as follows:

( i ) If required by the county road commission, the public utility or its subcontractor shall notify the county road commission, as soon as practical, of the location of the emergency public utility work and provide a statement that the vehicles that were used to perform the emergency utility work may have exceeded the loading maximums and gross vehicle weight requirements of subsection (12) as reduced under subsection (8). The notification may be made via facsimile or electronically.

( ii ) The public utility vehicle travels to and from the site of the emergency public utility work while on a restricted road at a speed not greater than 35 miles per hour.

(b) For nonemergency public utility work on restricted roads, as follows:

( i ) If the county road commission requires, the public utility or its subcontractor shall apply to the county road commission annually for a seasonal truck permit for roads under its authority before seasonal weight restrictions are effective. The county road commission shall issue a seasonal truck permit for each public utility vehicle or vehicle configuration the public utility or subcontractor anticipates will be utilized for nonemergency public utility work. The county road commission may charge a fee for a seasonal truck permit that does not exceed the administrative costs incurred for the permit. The seasonal truck permit must contain all of the following:

(A) The seasonal period requested by the public utility or subcontractor during which the permit is valid.

(B) A unique identification number for the vehicle and any vehicle configuration to be covered on the seasonal truck permit requested by the public utility or subcontractor.

(C) A requirement that travel on restricted roads during weight restrictions will be minimized and only utilized when necessary to perform public utility work using the public utility vehicle or vehicle configuration and that nonrestricted roads must be used for travel when available and for routine travel.

(D) A requirement that in the case of a subcontractor the permit is only valid while the subcontractor vehicle is being operated in the performance of public utility work.

(E) A requirement that a subcontractor vehicle or vehicle configuration must display signage on the outside of the vehicle to identify the vehicle as operating on behalf of the public utility.

( ii ) If the county road commission requires notification, the county road commission shall provide a notification application for the public utility or its subcontractor to use when requesting access to operate on restricted roads and the public utility or its subcontractor shall provide notification to the county road commission, via facsimile or electronically, not later than 24 hours before the time of the intended travel. A subcontractor using a vehicle on a restricted road shall have a copy of any notification provided to a county road commission in the subcontractor's possession while performing the relevant nonemergency work. Notwithstanding this subsection or an agreement under this subsection, if the county road commission determines that the condition of a particular road under its jurisdiction makes it unusable, the county road commission may deny access to all or any part of that road. The denial must be made and communicated via facsimile or electronically to the public utility or its subcontractor within 24 hours after receiving notification that the public utility or subcontractors intends to perform nonemergency work that requires use of that road. Any notification that is not disapproved within 24 hours after the notice is received by the county road commission is considered approved. The notification application required under this subparagraph may include all of the following information:

(A) The address or location of the nonemergency work.

(B) The date or dates of the nonemergency work.

(C) The route to be taken to the nonemergency work site.

(D) The restricted road or roads intended to be traveled upon to the nonemergency work site or sites.

(E) In the case of a subcontractor, the utility on whose behalf the subcontractor is performing services.

(7) The normal size of tires must be the rated size as published by the manufacturers, and the maximum wheel load permissible for any wheel must not exceed 700 pounds per inch of width of tire.

(8) Except as provided in this subsection and subsection (9), during the months of March, April, and May in each year, the maximum axle load allowable on concrete pavements or pavements with a concrete base is reduced by 25% from the maximum axle load as specified in this chapter, and the maximum axle loads allowable on all other types of roads during these months are reduced by 35% from the maximum axle loads as specified. The maximum wheel load must not exceed 525 pounds per inch of tire width on concrete and concrete base or 450 pounds per inch of tire width on all other roads during the period the seasonal road restrictions are in effect. Subject to subsection (5), this subsection does not apply to vehicles transporting agricultural commodities or, subject to subsection (6), public utility vehicles on a highway, road, or street under the jurisdiction of a local road agency, or a school bus. In addition, this subsection does not apply to a vehicle delivering propane fuel to a residence if the vehicle's propane tank is filled to not more than 50% of its capacity and the vehicle is traveling at not more than 35 miles per hour. The state transportation department and each local authority with highways and streets under its jurisdiction to which the seasonal restrictions prescribed under this subsection apply shall post all of the following information on the homepage of its website or, if a local authority does not have a website, then on the website of a statewide road association of which it is a member:

(a) The dates when the seasonal restrictions are in effect.

(b) The names of the highways and streets and portions of highways and streets to which the seasonal restrictions apply.

(9) The state transportation department for roads under its jurisdiction and a county road commission for roads under its jurisdiction may grant exemptions from seasonal weight restrictions for milk on specified routes when requested in writing. Approval or denial of a request for an exemption must be given by written notice to the applicant within 30 days after the date of submission of the application. If a request is denied, the written notice must state the reason for denial and alternate routes for which the permit may be issued. The applicant may appeal to the state transportation commission or the county road commission. These exemptions do not apply on county roads in counties that have negotiated agreements with milk haulers or haulers of other commodities during periods of seasonal load limits before April 14, 1993. This subsection does not limit the ability of these counties to continue to negotiate such agreements.

(10) The state transportation department, or a local authority with respect to highways under its jurisdiction, may suspend the restrictions imposed by this section when and where conditions of the highways or the public health, safety, and welfare warrant suspension, and impose the restricted loading requirements of this section on designated highways at any other time that the conditions of the highway require.

(11) For the purpose of enforcing this act, the gross vehicle weight of a single vehicle and load or a combination of vehicles and loads must be determined by weighing individual axles or groups of axles, and the total weight on all the axles is the gross vehicle weight. In addition, the gross axle weight must be determined by weighing individual axles or by weighing a group of axles and dividing the gross weight of the group of axles by the number of axles in the group. For purposes of subsection (12), the overall gross weight on a group of 2 or more axles must be determined by weighing individual axles or several axles, and the total weight of all the axles in the group is the overall gross weight of the group.

(12) The loading maximum in this subsection applies to interstate highways, and the state transportation department, or a local authority with respect to highways under its jurisdiction, may designate a highway, or a section of a highway, for the operation of vehicles having a gross vehicle weight of not more than 80,000 pounds that are subject to the following load maximums:

(a) Twenty thousand pounds on any 1 axle, including all enforcement tolerances.

(b) A tandem axle weight of 34,000 pounds, including all enforcement tolerances.

(c) An overall gross weight on a group of 2 or more consecutive axles equaling:

W=500[(LN)/(N-1)+12N+36]

W=500[(LN)/(N-1)+12N+36]

where W = overall gross weight on a group of 2 or more consecutive axles to the nearest 500 pounds, L = distance in feet between the extreme of a group of 2 or more consecutive axles, and N = number of axles in the group under consideration; except that 2 consecutive sets of tandem axles may carry a gross load of 34,000 pounds each if the first and last axles of the consecutive sets of tandem axles are not less than 36 feet apart. The gross vehicle weight must not exceed 80,000 pounds including all enforcement tolerances. Except for 5 axle truck tractor, semitrailer combinations having 2 consecutive sets of tandem axles, vehicles having a gross weight in excess of 80,000 pounds or in excess of the vehicle gross weight determined by application of the formula in this subsection are subject to the maximum axle loads of subsections (1), (2), and (3). As used in this subsection, "tandem axle weight" means the total weight transmitted to the road by 2 or more consecutive axles, the centers of which may be included between parallel transverse vertical planes spaced more than 40 inches but not more than 96 inches apart, extending across the full width of the vehicle. Except as otherwise provided in this section, vehicles transporting agricultural commodities have the weight load maximums under this subsection.

(13) The axle loading maximums under subsections (1), (2), (3), and (4) are increased by 10% for vehicles transporting agricultural commodities or raw timber, excluding farm equipment and fuel, from the place of harvest or farm storage to the first point of delivery on a road in this state. However, the axle loading maximums as increased under this subsection do not alter the gross vehicle weight restrictions under this act. This subsection does not apply to either of the following:

(a) A vehicle utilizing an interstate highway.

(b) A vehicle utilizing a road that is subject to seasonal weight restrictions under subsection (8) during the time that the seasonal weight restrictions are in effect.

(14) Notwithstanding any other provision of this section, a vehicle or combination of vehicles that have a gross weight of 82,000 pounds or less and that is operated by an engine that is fueled wholly or partially by compressed or liquefied natural gas may exceed the axle loading maximums under subsections (1), (2), (3), and (4) and the weight load maximums under subsection (12) by an amount equal to the difference between the weight of the vehicle attributable to the natural gas tank and fueling system carried by that vehicle and the weight of a comparable diesel tank and fueling system. A vehicle or combination of vehicles described in this subsection may exceed the axle loading maximums under subsections (1), (2), (3), and (4) and the weight load maximums under subsection (12) by a total of not more than 2,000 pounds for all axles of the truck, truck tractor, or power unit.

(15) Notwithstanding any other provision of this section, a vehicle or combination of vehicles that have a gross weight of 82,000 pounds or less and that are powered wholly or partially by electric batteries may exceed the axle loading maximums under subsections (1), (2), (3), and (4) and the weight load maximums under subsection (12) by a total of not more than 2,000 pounds for all axles of the truck, truck tractor, or power unit.

(16) As used in this section:

(a) "Agricultural commodities" means those plants and animals useful to human beings produced by agriculture and includes, but is not limited to, forages and sod crops, grains and feed crops, field crops, dairy and dairy products, poultry and poultry products, cervidae, livestock, including breeding and grazing, equine, fish, and other aquacultural products, bees and bee products, berries, herbs, fruits, vegetables, flowers, seeds, grasses, nursery stock, mushrooms, fertilizer, livestock bedding, farming equipment, fuel for agricultural use, and maple sap. Agricultural commodities do not include trees or lumber.

(b) "Emergency public utility work" means work performed to restore public utility service or to eliminate a danger to the public due to a natural disaster, an act of God, or an emergency situation, whether or not a public official has declared an emergency.

(c) "Farm storage" means any of the following:

( i ) An edifice, silo, tank, bin, crib, interstice, or protected enclosed structure, or more than 1 edifice, silo, tank, bin, crib, interstice, or protected enclosed structure located contiguous to each other.

( ii ) An open environment used for the purpose of temporarily storing a crop.

(d) "Public utility" means a public utility under the jurisdiction of the public service commission or a transmission company.

(e) "Public utility vehicle" means a vehicle owned or operated by a public utility or operated by a subcontractor on behalf of a public utility.

(f) "Transmission company" means either an affiliated transmission company or an independent transmission company as those terms are defined in section 2 of the electric transmission line certification act, 1995 PA 30, MCL 460.562.

History: 1949, Act 300, Eff. Sept. 23, 1949; Am. 1965, Act 36, Imd. Eff. May 19, 1965; Am. 1967, Act 277, Eff. Nov. 2, 1967; Am. 1974, Act 348, Imd. Eff. Dec. 21, 1974; Am. 1975, Act 270, Imd. Eff. Nov. 10, 1975; Am. 1978, Act 385, Imd. Eff. July 27, 1978; Am. 1978, Act 510, Eff. Aug. 1, 1979; Am. 1980, Act 217, Imd. Eff. July 18, 1980; Am. 1980, Act 487, Imd. Eff. Jan. 21, 1981; Am. 1982, Act 206, Imd. Eff. July 1, 1982; Am. 1984, Act 74, Imd. Eff. Apr. 18, 1984; Am. 1988, Act 346, Eff. Jan. 1, 1989; Am. 1993, Act 22, Imd. Eff. Apr. 14, 1993; Am. 2000, Act 6, Imd. Eff. Feb. 24, 2000; Am. 2002, Act 41, Imd. Eff. Mar. 12, 2002; Am. 2006, Act 83, Imd. Eff. Mar. 29, 2006; Am. 2006, Act 658, Imd. Eff. Jan. 10, 2007; Am. 2008, Act 579, Imd. Eff. Jan. 16, 2009; Am. 2009, Act 146, Imd. Eff. Nov. 19, 2009; Am. 2012, Act 252, Imd. Eff. July 2, 2012; Am. 2012, Act 498, Eff. Mar. 28, 2013; Am. 2012, Act 522, Imd. Eff. Dec. 28, 2012; Am. 2016, Act 72, Eff. July 4, 2016; Am. 2017, Act 80, Eff. Oct. 9, 2017; Am. 2018, Act 273, Eff. Sept. 27, 2018; Am. 2018, Act 274, Eff. Sept. 27, 2018; Am. 2024, Act 106, Eff. Apr. 2, 2025