Iowa OSOW Regulations (Iowa DOT)
Legal Dimensions (No Permit Required)
- Width: 8'6"
- Height: 14'6" (Iowa allows 14'6" legal height)
- Length: 75' maximum
Legal Weights (No Permit Required)
- Gross vehicle weight: 80,000 lbs maximum
- Standard federal bridge formula applies
General Permit Provisions
Permit Holder Responsibilities
- State assumption of responsibility: The State of Iowa, Iowa DOT, and any permit issuing authority assume NO responsibility for the property of the permit holder
- Safety obligations: During movement under permit, permit holder must:
- Meet all terms and conditions of the permit
- Take all reasonable precautions to protect and safeguard the lives and property of the traveling public and adjacent property owners
Insurance Requirements
Required public liability insurance coverage:
- $100,000 bodily injury each person
- $200,000 bodily injury each occurrence
- $50,000 property damage
Documentation:
- Current certificate of public liability insurance must be carried in the vehicle for which the permit has been issued
- Proof of liability insurance may be in writing or in electronic format
Permit Conditions
Important restrictions:
- Nothing shall exempt the permit holder from compliance with any load limitations established on bridges or roads posted with embargo signs
- Permit void if: Actual weights or dimensions exceed what is indicated on the permit or its revisions
- Non-divisible loads only: Permits can be issued only for loads that are a single article that cannot be reasonably broken down to make it legal in size and weight
- Permit location: Must be carried in the cab of the vehicle for which it has been issued and be available for inspection
Route Planning Requirements
Annual permit holders must check routes prior to moving:
- Vertical clearance maps
- Bridge embargo maps
- Pavement restriction maps
- 511ia.org website for construction restrictions and clearance problems
- Maps available at: iowadot.gov/mvd/motorcarriers
Permitted Tandem Axle Weights
Vehicles operating under permits issued pursuant to Iowa Code 321E.8, 321E.9, or 321E.9A:
Tandem axle weight allowances:
- Gross weight not to exceed 46,000 lbs on a single-tandem axle of the truck tractor
- Gross weight not to exceed 46,000 lbs on a single-tandem axle of the trailer or semitrailer
Conditions:
- Each axle of each tandem group must have at least 4 tires
- No single axle of the tandem group may exceed 24,000 lbs
- If tandem axle is within a larger group of axles: Maximum weight of that specific group shall not exceed 20,000 lbs per axle
Escort Vehicle Requirements
Escort Operator Requirements
Required qualifications:
- Age: At least 18 years old
- License: Valid Class A, B, C, or D driver's license
- Insurance: Must carry proof of public liability insurance in the amounts of $100,000/$200,000/$50,000
Escort Vehicle Specifications
Vehicle requirements:
- Must be approximately the size of a normal passenger automobile or pickup
- Must have a flashing or strobe amber light that shall be burning while escorting a permit load
- Restriction: Escorting vehicle shall NOT be used to tow a trailer while performing escorting duties
Required Warning Devices and Escort Requirements
Detailed requirements by dimension:
| Dimension | Flags/Signs | Lights | Escort - Four-Lane | Escort - Two-Lane |
|---|---|---|---|---|
| Length | ||||
| 75'1" up to 85' | Yes | Not required | Not required | Not required |
| Over 85' up to 120' | Yes | Yes | Not required | Not required |
| Over 120' | Yes | Not required | Rear | Rear |
| Projections | ||||
| Front: over 25' | Not required | Yes | Not required | Not required |
| Rear: over 4' up to 10' | Flags only | Not required | Not required | Not required |
| Rear: over 10' | Flags only | Yes | Not required | Not required |
| Height | ||||
| Over 14'6" up to 20' | Yes | Not required | Front with height pole | Front with height pole |
| Weight | ||||
| Over 80,000 lbs | Not required | Yes | Not required | Not required |
| Width | ||||
| Over 8'6" up to 12' | Yes | Not required | Not required | Not required |
| Over 12' up to 14'6" | Yes | Not required | Rear* | Front* |
| Over 14'6" up to 16'6" | Yes | Not required | Rear* | Front |
| Over 16'6" up to 18' | Yes | Not required | Rear | Front |
*Lighting Alternative: In lieu of an escort, a vehicle can display an amber light or strobe on the power unit and on the rear extremity of the load.
Lighting Requirements
Flashing or strobe amber light required:
- Mounted on the towing unit
- Visible for at least 500 feet
- Provides 360-degree warning
Alternative:
- An escort can be used in lieu of amber light (for certain width categories)
Transport Vehicle Requirements
Signs
"Oversize Load" sign specifications:
- Size: At least 18 inches high by 7 feet long
- Lettering: Minimum 10-inch black letters with 1.5-inch stroke
- Background: Yellow
- Mounting:
- One on the front bumper
- One on the rear of the load
- Mobile homes: Rear sign must be mounted at least 7 feet above the highway surface (measured from bottom of sign)
- Removal requirement: Signs or warning devices must be mounted so they can be removed or covered when the vehicle is within legal dimensions
Flags
Flag specifications:
- Color: Red or orange fluorescent
- Size: At least 18 inches square
Flag placement:
- One flag at each front corner of the towing unit
- One flag at each rear corner of the load
- One flag at any additional protrusion in the width of the load
Operating Times
Standard Hours
- Movement allowed: 7 days a week
- Time window: 1/2 hour before sunrise to 1/2 hour after sunset
- Exceptions: Designated holidays and special events with abnormally high traffic counts
Holiday Restrictions
No movement allowed on the following designated holidays:
- Memorial Day
- Independence Day (July 4th)
- Labor Day
Additional restriction:
- No movement after 12 noon on days preceding these holidays and holiday weekends that include holidays falling on Monday
- Exception: As provided for in Iowa Code 321.457
Continuous Moves (Night Travel)
Vehicles and loads may travel by permit between 1/2 hour after sunset and 1/2 hour before sunrise if the following conditions are met:
Dimensional Limits for Night Travel
- Width: Not to exceed 11 feet
- Height: Not to exceed 14 feet, 6 inches
- Length: Not to exceed 100 feet
- Weight: Within permitted axle limits
Roadway Requirements
- Travel must be on roadways with:
- Minimum width of 22 feet
- Minimum lane width of 11 feet
Safety Lighting for Continuous Moves
Safety lighting must be provided at the widest part of the load.
Lamps may be placed:
- At the outer ends of the load itself, OR
- On appurtenances that are equal in width to the widest part of the load
- Positioned at both extreme front and rear of the vehicle or trailer
Required safety lighting:
- Rear lighting: One lighted red lamp on each side at the rear of the load
- Front lighting: One lighted yellow or amber lamp on each side at the front of the load
Electronic Permits
- Iowa accepts electronic permits
- Valid on smartphones or tablets
- No minimum screen size requirement
Contact Information
- Phone: (515) 237-3268
- Website: https://iowadot.gov/mvd/motorcarriers/oversize-overweight-trip-permits
- State: Iowa
- Agency: Iowa Department of Transportation (Iowa DOT)
- Division: Motor Vehicle Division - Motor Carriers
Regulatory References
- Iowa Department of Transportation
- Iowa General Provisions for Oversize Load Permit - Form 442052 (01-19)
- Iowa Code 321.457 (Holiday movement exceptions)
- Iowa Code 321E.8, 321E.9, 321E.9A (Permitted tandem axle weights)
- 511ia.org (Road conditions and construction restrictions)
- iowadot.gov/mvd/motorcarriers (Maps: vertical clearance, bridge embargo, pavement restrictions)
- https://iowadot.gov/mvd/motorcarriers/motorcarriers/osowpermits_determine
- https://iowadot.gov/mvd/motorcarriers/oversize-overweight-trip-permits
- https://jjkellercompliancenetwork.com/regsense/oversize-and-overweight-movements-iowa
Last Updated: 2025-11-11