Idaho Oversize and Overweight Trucking Permits

The Idaho Transportation Department (ITD) regulates the movement of oversize and overweight (OSOW) loads via the Division of Motor Vehicles. Carriers must obtain a permit whenever a vehicle or load exceeds the legal dimensions defined in Idaho Code Title 49, Chapter 10. Legal limits for standard operations are 8 feet 6 inches in width, 14 feet in height, and 75 feet in length for most combinations. Gross vehicle weight is restricted to 80,000 pounds on Interstates and up to 105,500 pounds on designated state highways, provided the vehicle meets the Federal Bridge Formula requirements. DispatchTool assists carriers in managing these complex requirements by integrating IFTA reporting and specialized route documentation into a single dashboard. By using DispatchTool, operators can store state-specific permit PDF documents directly within the load file, ensuring drivers have immediate access to ITD-issued provisions during roadside inspections or at weigh stations like those on I-84 or I-15. Create a DispatchTool account to centralize your state permit records and compliance tracking.

Legal Dimensions and Weight Thresholds

In Idaho, any vehicle exceeding a width of 8 feet 6 inches requires a special permit. The legal height limit is 14 feet; however, carriers must be aware that specific clearances on secondary routes may be lower. The maximum legal length for a single unit is 45 feet, while a tractor-semitrailer combination is generally limited to 75 feet overall length. Weight limits follow the Idaho Bridge Formula. A standard five-axle configuration is allowed a maximum of 80,000 pounds. Single axles are limited to 20,000 pounds, and tandem axles are capped at 34,000 pounds. If your load exceeds any of these specific metrics, you must apply for an Overweight or Oversize permit through the ITD ITD-1011 form process.

Idaho Permit Types and Fees

ITD offers several permit types based on the frequency and nature of the move. A Single Trip Permit is valid for five days and typically costs $28.00 for oversize loads. For overweight loads, the fee includes the base $28.00 plus additional mills-per-mile charges based on the weight exceeding 80,000 pounds. Annual permits are available for specific dimensions, such as the Annual Oversize Permit which costs $43.00 and allows for widths up to 14 feet 6 inches on designated routes. For heavy haulers, an Annual Excess Weight Permit costs $43.00, but it is restricted to specific weight brackets and does not exempt the carrier from registering for the appropriate higher weight tier.

Pilot Car and Escort Requirements

Escort vehicle requirements in Idaho are triggered by the dimensions of the load and the type of highway. For loads exceeding 12 feet in width on two-lane highways, one front escort is mandatory. If the width exceeds 14 feet, two escorts (front and rear) are required. On interstate highways, a rear escort is generally required only once the width exceeds 15 feet. Loads exceeding 100 feet in length on two-lane roads require a rear escort. Additionally, any load exceeding 16 feet in height must have a front escort equipped with a height pole to ensure clearance under Idaho’s bridge infrastructure and utility lines.

Signage, Lighting, and Red Flag Rules

All oversize loads must display 'Oversize Load' signs on the front and rear of the vehicle. These signs must be at least 7 feet wide and 18 inches high, with black letters 10 inches high on a yellow background. Idaho also requires 18-inch square red or fluorescent orange flags to be placed at the four corners of the extremities of any wide load. When operating during nighttime or periods of poor visibility, the extremities must be marked with amber lights to the front and side, and red lights to the rear. Failure to comply with Idaho Code 49-944 regarding lighting can result in immediate shutdown of the movement by the Idaho State Police.

Restricted Travel Times and Holidays

Movement of oversize loads in Idaho is generally restricted to daylight hours, defined as one-half hour before sunrise to one-half hour after sunset. However, loads that are only overweight (legal dimensions) or loads exceeding width only up to 10 feet may be allowed 24-hour travel. Major holiday periods, including New Year’s Day, Memorial Day, Independence Day, Labor Day, Thanksgiving, and Christmas, typically involve a total prohibition on OSOW movement starting at 2:00 PM the day before the holiday. Specific urban areas like Boise, Coeur d'Alene, and Idaho Falls may have additional 'curb time' restrictions during morning and evening rush hours (7:00–9:00 AM and 4:00–6:00 PM).

129,000 Pound Long Combination Vehicles

Idaho allows for Long Combination Vehicles (LCVs) to operate at gross weights up to 129,000 pounds on designated routes. To operate at this weight, carriers must obtain a specific 129K permit and the vehicle must have a minimum of 8 axles. The route must be pre-approved by the Idaho Transportation Board. The permit fee for a 129,000-pound single trip is calculated using the standard overweight formula, while annual permits provide a cost-effective option for frequent runs between the Port of Lewiston and southern Idaho distribution centers. Off-system routes may require additional coordination with local highway districts.

Sources

Idaho Transportation Department - Overweight/Oversize Permits (2024) — https://itd.idaho.gov/dmv/poe/permits.html Idaho Statutes Title 49 Chapter 10 (2024) — https://legislature.idaho.gov/statutesrules/idstat/Title49/T49CH10/ American Transportation Research Institute (ATRI) - Idaho State Profile (2023) — https://truckingresearch.org/

Frequently asked

How much does a single-trip oversize permit cost in Idaho?

A standard single-trip oversize permit costs $28.00 and is valid for a period of 5 consecutive days.

At what width is a pilot car required on Idaho two-lane roads?

A front pilot car is required for any load exceeding 12 feet in width on two-lane highways in Idaho.

What is the maximum legal height in Idaho without a permit?

The maximum legal height is 14 feet. Anything exceeding this height requires a permit and potentially a height-pole escort.

Does Idaho allow oversize movement on Sundays?

Yes, Idaho generally allows movement on Saturdays and Sundays for loads up to 10 feet wide, provided they do not exceed other dimension limits or holiday restrictions.

What is the weight limit for a tandem axle in Idaho?

The legal limit for a tandem axle is 34,000 pounds, as per the Federal Bridge Formula adopted in Idaho Code.