Legal size limits without a permit
| Measurement | Idaho legal limit |
|---|---|
| Height | 14 ft |
| Width | 8'6" |
| Front Overhang | Confirmed at filing |
| Rear Overhang | Confirmed at filing |
Axle and gross weights
How much each axle group and the whole vehicle can carry in Idaho, without a permit and with an overweight permit.
| Axle group | Legal limit | With a permit |
|---|---|---|
| Steer axle | Confirmed at filing | Confirmed at filing |
| Single axle | 20,000 lbs | Up to 33,000 lbs on 'black'-coded routes (varies by route color) |
| Tandem axle | 34,000 lbs | Up to 56,000 lbs on 'black'-coded routes; formula-based on other route colors |
| Tridem axle | Confirmed at filing | Confirmed at filing |
| Quad axle | Confirmed at filing | Confirmed at filing |
| Gross weight | 80,000 lbs | 129,000 lbs on designated routes (Extra Length/Excess Weight Annual Permit) |
Superload: Loads exceeding 250,000 lbs require extended bridge analysis; loads over 800,000 lbs require third-party engineering analysis
Permit types we file in Idaho
Oversize-Only / Overweight-Oversize Non-Divisible PermitSingle-trip or annual permit for non-divisible loads.
Extra Length-Excess Weight Annual PermitAnnual permit for divisible loads and extra-length combinations up to 129,000 lbs on designated routes.
Manufactured Homes/Modular Buildings PermitsSpecial-use annual permits for mobile/modular housing and farm equipment.
Maximum dimensions with a permit
| Dimension | Maximum with a permit |
|---|---|
| Length | 115-120 ft on 'black'-coded routes |
| Width | 14 ft ('black' routes); 12'6" ('red' routes) |
| Height | 15'6" on 'black'/interstate routes |
| Rear Overhang | 4 ft triggers mandatory lighting/flagging |
Loads exceeding 250,000 lbs move into ITD's extended bridge-analysis review, and loads over 800,000 lbs require third-party structural engineering analysis.
Escorts and travel restrictions
Escort & pilot car rules
- Front escort with height pole required for loads over 16' wide on red/black routes.
- Rear escort required if the load obstructs the driver's rearward visibility 200+ feet.
- Mandatory escort for width over 14 ft (red routes) or height over 16 ft.
When you can travel
- Red-coded routes: daylight-only travel; no weekend travel.
- Black-coded/interstate routes: near 24/7 travel for loads ≤12' wide, ≤120' long, ≤15' high.
- Rush-hour ban: loads over 13' wide prohibited 6-9am and 4-6:30pm weekdays in major cities.
- Seasonal spring break-up restrictions reduce allowable per-axle weights to 12,000-16,000 lbs.
Signs, flags and lights
Most states require
- An “OVERSIZE LOAD” banner on the front of the truck and the rear of the load.
- Red or fluorescent orange warning flags at each corner and at the widest points of the load.
- Amber warning lights or clearance lights when moving at night, where night travel is allowed.
Idaho specifics
- Banner size, flag size and light rules for Idaho are listed on your permit.
- We include them in your permit notes so your driver has them before the trip.
Rules change. Limits and requirements are set by ITD and can change. We confirm the current rules for your exact load before filing.