Idaho OS/OD Overview
Permit Required
Yes – all oversize or overweight loads require a permit from the Idaho Transportation Department (ITD).
Legal Limits (Without Permit)
- Width: 8'6"
- Height: 14'
- Length: 75' (combo); 53' single trailer
- Weight: 80,000 lbs GVW (with standard axle limits)
Permitted Load Maximums (Typical Upper Limits)
- Width: Up to 16' or more with proper escorting
- Height: Over 15'6" requires route survey and clearance
- Length: Up to 120'+ depending on route
- Weight: Over 250,000 lbs with engineering and structure analysis
Superloads require pre-approval, route analysis, and possible pilot car coordination.
Travel Hours
- Standard: Sunrise to sunset for most oversize loads
- Weekend: Travel allowed for some loads under 10' wide and 100' long
- Holidays: No travel on major holidays
- Night travel: May be approved for loads under 10' wide with lighting
Escort Requirements (General Guidelines)
| Dimension | Escort Requirement |
|---|---|
| Width > 12' | 1 Escort (front or rear depending on route) |
| Width > 14' | 2 Escorts (front and rear) |
| Height > 15'6" | High pole escort and route clearance |
| Length > 100' | 1 Rear Escort (2 if over 120') |
Additional Notes
- Oversize Load signs, red flags, and amber lights required as specified in permit
- Mountain routes and weather conditions can affect movement—chains may be required
- Permits are processed through the ITD online permit system (Port of Entry offices also assist)
Detailed Information
PERMITS: Permits valid for five days.
OPERATING TIME: One half hour before sunrise to one-half hour after sunset, including Saturdays and Sundays (majority of routes). Up to and including 10' wide, 110' long or 14'6 high, travel is allowed 24/7 (majority of routes) with lighting as specified on permit. Weekend travel is allowed on majority of routes during daytime hours.
RESTRICTED TRAVEL: If over 13' wide, movement prohibited between 6:30 – 8:30 a.m., 11:30 – 1:30 p.m., and 4:00 – 6:00 p.m. in Boise, Caldwell, Coeur d'Alene, Idaho Falls, Lewiston, Nampa, Pocatello, Twin Falls, Garden City and Chubbuck. Holiday travel restrictions may depend on dimension.
LEGAL DIMENSIONS: Width: 8'6" Height: 14' Length: 53' semi-trailer on National Network, 48' trailer on non N.N. (“non-designated”) Note: Several 2-lane highways in Idaho are non-designated, including US-12 except in the Lewiston to Spalding, US-93 from Salmon to Challis, and US-95 from Council to Grangeville. For divisible loads, trailers exceeding 48’ are only allowed with an annual extra length permit, and the tractor-trailer off-track measurement must not exceed 5.50 feet (3.00 on a few mountain routes). Non-divisible loads are covered by single or annual permit, without regard to off-track amount. Overhang: 4' front, 15' rear Weight: 80,000 Gross Single – 20,000 Tandem – 34,000 Tridem – depends on spacings Steer – 600 pounds per inch of tread width (13,200 pounds with 11" tires). Divisible Loads Exceeding 80,000: You can exceed 80,000 gross without a permit on state highways as long as you are legal on all axle/group weights and you are licensed for at least the amount of your gross weight. However, if you need any Interstate routes, you will need to get an Annual Excess Weight Permit.
ROUTINE PERMIT LIMITS:
Width: 16' Height: 15'6 Length: 110'. Weight: Single – 33,000 to 22,000* Tandem – 56,000 to 38,500* Tridem – 70,500 to 48,000* Steer – 600 pounds per inch of tread width (13,200 pounds for 11" tires)
* Group weight maximums depend on route classification, with Interstate routes getting the highest.
Loads exceeding these dimensions or are considered as Super Loads.
ESCORTS:
On 2-Lane Highways: Width: Over 12' – 1 escort; over 14' – 2 escorts; over 16' – may require 3 escorts
Height: Over 16' – 1 escort. Length: Over 100' – 1 escort. Overhang: Over 25' rear – 1 escort.
On Interstate System: Width: Over 15' – 1 escort; over 16' – may require 2 or 3 escorts Height: Length: Over 120' – 1 escort. Overhang: Over 25' rear – 1 escort. Over 16' – 1 escort.
MISCELLANEOUS: All lift axles must be on the ground if exceeding legal axle weights. Blades, buckets, etc. may be taken off and hauled on the same load, depending on route and situation. State will determine on a case by-case basis.
SIGNS, FLAGS & LIGHTS: Requirements are specified on Idaho permit. "Oversize Load" signs are required on all overwidth loads. Flags are required on all four corners and extremities of overwidth loads and on rear overhang exceeding 4'. Overweight only loads do not require signs or flags.