A green tractor and trailer driving on a road as a large pickup truck passes in the opposite direction

IoH Information

Definition s. 340.01 (24) (a) Wis. Stats.

The definition of an Implement of Husbandry reads:

  1. Subject to par. (b), “implementation of husbandry” means all of the following:
    1. A self-propelled or towed vehicle that is manufactured, designed, or reconstructed to be used and that is exclusively used in the conduct of agricultural operations. An “implementation of husbandry” may include any of the following:
      1. Farm tractor (Referred to as Category A).
      2. Self-propelled combine, self-propelled forage harvester; self-propelled fertilizer or pesticide application equipment but not including manure application equipment; towed or attached tillage, planting, harvesting, and cultivation equipment and its towing farm tractor or other power unit; to which it is attached; or another self-propelled vehicle that directly engages in harvesting farm products, directly applies fertilizer, spray or seeds but not manure, or distributes feed to livestock. (Referred to as Category B).
      3. A farm wagon, farm trailer, grain cart, manure trailer, or trailer adapted to be towed by, or to tow or pull, another implement of husbandry (Referred to as Category C).
    2. A combination of vehicles in which each vehicle in the vehicle combination is an IoH or in which an IoH is towed by a farm truck, farm truck tractor, motor truck, or agricultural commercial vehicle.
  2. Implement of husbandry does not include any of the following:
    1. An agricultural commercial vehicle (Ag CMV).
    2. A vehicle that, notwithstanding s. 340.01 (8) Wis. Stats., is a commercial motor vehicle (CMV) under 49 CFR 390.05.


  • No width limitations when operated or towed but additional width requirements when trailered.
  • Additional lighting and marking requirements for wide IoH were effective November 1, 2015.
  • Also applies for IoH being operated, towed or trailered for delivery, service, or repair by dealer or farmer within 75-mile radius of business or farm.


  • No height limitations for IoH operating or towed on any highway or when trailered.
  • Operator of IoH remains responsible for ensuring safe clearance of any overhead obstructions.


For vehicles or vehicle combinations that exceed these length limits, a No Fee Permit may be available.

  • Single Vehicle
    • 60 feet
  • 2 vehicle combination — one towed IoH unit drawn by an IoH power unit
    • 100 feet
  • 3 vehicle combination or agricultural trains — two towed IoH units and power unit.
    • No more than 100 feet with speed restriction of 25 mph or less or 70 feet at a speed greater than 25 mph.
    • Towed IoH units being drawn by a motor truck, truck tractor, or agricultural commercial motor vehicle (Ag CMV) must be empty. “Empty” means less than 20% full.
    • Additional lighting and marking requirements apply on agricultural trains.

Length Exception: Irrigation System

  • There is no length limit for an irrigation system being towed by a farm tractor, farm truck, farm truck tractor or motor truck temporarily operated upon a highway. [s. 348.07 (2) (e) 3 Wis. Stats.]

IoH/Ag CMV Maximum Weight Limits table [s. 348.15 (3) (g) Wis. Stats.] applies. This allows for a maximum single axle weight of 23,000 pounds and a gross vehicle weight of 92,000 pounds dependent upon on number of axles and axle spacing.

  • 23,000 pounds axle weight and 92,000 pounds GVW apply to all IoH (no Category B exemption) on state and US highways.
  • IoH weight limits do not apply on Interstate Highways except for the I 41 corridor. [s. 348.15 (9) (d) Wis. Stats.]
  • All operators must abide by seasonal and other special road postings or bridge postings.

To operate at weights greater than those listed in the Maximum IoH/Ag CMV Weight Limit Table, you may need to apply for a No Fee Permit from the maintaining authority for the highways on which you are proposing to operate.

Weight Exemptions

  • An empty self-propelled or towed potato harvester being operated, transported, or trailered is exempt from axle weight limit and Class B road postings.
  • IoH Category B are exempt from:
    • axle weight limits unless the local maintain authority passes an ordinance or resolution limiting IoH Category B axle weight. See Permits. 
    • GVW and axle weight limits when operated, towed or trailered between fields and operated on the highway for a distance of .5 mile or less.
    • Class B road postings.
  • An IoH operated, towed or transported for delivery, service, repair by dealer or farmer within 75-mile radius of business or farm is exempt from GVW and axle weight limits. Also exempt from Class B road postings.

A handout for printing is available here: lighting and marking for IoH 2.9.18.

Lighting and marking of implements of husbandry (IoH) are valuable safety features when operating on public roads. New regulations were effective November 1, 2015. Many pieces of farm machinery have already been manufactured with the lighting and marking requirements that are now reflected in the law. Please see this video from WisDOT about lighting requirements for all IoH.

Hours of Darkness

  • Hours of Darkness is the period of time from one-half hour after sunset to one-half hour before sunrise and all other times when there is not sufficient natural light to render clearly visible to any person or vehicle upon a highway at a distance of 500 feet.
  • For non-wide IoH, lighting and marking requirements are required during hours of darkness.
  • Wide IoH law for lighting require lights or lamps to be activated at all times vehicle (s) are operated on the highway.
  • SMV emblems are required at all times.
  • Wisconsin law does not define hours of daylight.

s. 340.01 (23) Wis. Stats.

Marking Requirements

Slow Moving Vehicle Emblem

  • A slow-moving vehicle (SMV) emblem is a required marking on any type of IoH, including animal drawn, that usually travels at speeds less than 25 mph.
  • It is to be displayed at all times on the most visible rear area of the vehicle or combination of vehicles. If a SMV emblem on a power unit is visible from rear and in compliance, then the towed units are not required to have an SMV emblem. It is allowable for two or three vehicle combinations to have more than one SMV emblem.
  • These emblems should be mounted pointing upward perpendicular to route of travel, with the lower edge 2 to 6 feet off the ground, and either centered or as near to the left of center of the equipment as practical.
  • SMV emblems must be bright and clean, and should be replaced if faded.

s. 347.245 Wis. Stats.

Lighting Requirements for vehicles not meeting the wide IoH definition

Lights or lamps in the table below must be activated when operating on the road or parked in the right-of-way during hours of darkness.

Self-Propelled IoH including tractors

  • 2 white headlights·
  • At least 1 red tail lights If purchased with 2 red tail lights both must be working.
  • Tail lights are to be mounted 20-72 inches off the ground.·
  • Work lights are prohibited for use on road or when parked in right-of-way.

Towed IoH

  • 2 red tail lights or 2 red reflectors on the rear.(If manufactured before 1984, these IoHs are allowed to have only 1 lamp or 2 red reflectors on the rear.)
  • Towed IoH that is more than 4 feet wide to the left side of the hitch must have an amber reflector at the widest point on the left side facing forward to warn on-coming traffic.

3- vehicle trains

  • 1 red light or red or amber reflector must be located on the left and right side of every vehicle in the train visible from a minimal distance of 500 feet.

Animal-drawn vehicle

  • 1 white lamp visible from the front
  • 2 red lamps or lanterns visible from the rear marking the width of the vehicle visible for 500 feet and mounted to indicate extreme width of the vehicle.

Wide IoH

In addition to the current requirements for lighting and marking the following requirements apply based on the width of the IoH. Please see this video from WisDOT about lighting requirements for wide IoH.

Self-propelled including farm tractors in excess of 12 feet

  • Must be equipped with a 360−degree yellow or amber rotating strobe or beacon light, mounted at the highest practicable point, OR
  • 2 flashing amber lights visible to the front and rear
  • Activated at any time when operated on the road or parked in the right-of-way

Note: Any attachment to a self-propelled IoH or farm tractor is included in the vehicle’s width.

Wide IoH, in excess of 15 feet or that extend over the center of the roadway into a lane intended for the opposite direction of travel

  • Option A: At all times when operating on highway
    • At least 2 amber flashing warning lamps, visible from both the front and rear. Must be mounted, as nearly as practicable, to indicate the extreme width but not more than 16 inches from the lateral extremities.
    • Red retroreflective material, visible to the rear and mounted within 25 inches of the extreme left and extreme right of the IoH, spaced as evenly as practicable.
    • At least 2 strips of yellow retroreflective material visible to the front. On left and right sides of IoH, the outer edge of this material shall be mounted within 16 inches of the extreme left and extreme right of the IoH.
    • At least 2 red tail lamps mounted to the rear of the IoH, or as close to the rear as practicable. Not required to be wired to light when headlamps or other lamps light.
  • Option B: At times other than darkness, a wide IoH, may be operated on highway if all of the following apply:
    • Is accompanied by an escort vehicle operating with hazard lights activated.
    • 2 orange or red flags, not less than 12 inches square, are attached to the rear of the wide IoH, or as close to the rear as practicable to mark extreme left and extreme right of IoH.

In addition, IoH wider than 22 feet traveling greater than .5 mile, must have an escort with hazard lights activated:

  • When operated on highway with one lane of travel in each direction escort vehicle shall operate ahead of wide IoH.
  • When operated on a highway with more than one lane for travel in each direction or on a 3-lane highway, escort vehicle shall operate behind wide IoH.


IoH and being transported by a 2 vehicle combination trailer or semi-trailer need to follow these lighting and marking requirements:

  • 2 flashing amber warning lights activated while IoH is being transported, visible to the front and rear, and mounted to indicate the extreme width while being transported.
  • Self-propelled IoH and farm tractors exceeding 12 feet in width, a yellow or amber rotating strobe or beacon light or 2 flashing amber warning lights visible to front and rear must be activated.

An IoH may be transported by a 2-vehicle combination with a trailer or semi-trailer to or from a farm-related destination at the same height, length and weight limits as if being driven on the highway outside the hours of darkness [s. 340.01 (24) (a) 1b Wis. Stats.]. IoH Category B retain weight exceptions if transported by a 2-vehicle combination via trailer or semi-trailer to or from a farm-related destination.

During hours of darkness width is limited to 8 feet 6 inches [s. 348.05 (3m) Wis. Stats.]. The maximum width for an IoH being trailered on the Interstate system, at any time, is 8 feet 6 inches. Contact the Wisconsin Department of Transportation regarding oversize permits as the No Fee Permit does not cover width limits.

Any IoH being trailered wider than 8 feet 6 inches requires 2 flashing amber lights visible front and rear at the extremities of the IoH.

See Permits section for any IoH being trailered that exceed any size and weight dimension.

For purposes of delivery, repair, or servicing within 75 mile radius of the farmer’s owned or leased land, or dealer’s business location:

  • The same width and length laws with lighting and marking for IoH apply.
  • No weight limits for an IoH or Ag CMV while being operated, towed or transported by an implement dealer or farmer.
  • May operate on Class B roads at increased weights but must obey seasonal and special postings.
  • Projecting loads limits on side of vehicles (s. 348.09 Wis. Stats.) does not apply if the load is an IoH or Ag CMV being transported or operated by dealer or by farmer for delivery or repair. The vehicle being transported may be centered on the transporting vehicle.

s. 100.47 (3) Wis. Stats.

  1. Disclosure
    1. No person in the business of selling farm equipment may sell farm equipment that can be operated on a highway unless, at the time of sale, the person who sells the farm equipment discloses to the buyer in writing the gross vehicle weight and axle weights of the unladen farm equipment at the point of sale.
  2. Exceptions. Subsections (2) and (3) (b) do not apply to:
    1. Sales of farm equipment to another person in the business of selling farm equipment for the purpose of resale.
    2. Sales of farm equipment for the purpose of salvage.
    3. Sales by auction, unless the auctioneer holds title to the farm equipment being sold.
  3. Penalty. Any person who violates this section may be required to forfeit not more than $500 for each violation.