Published
Oversize load permits: the number comes before the wheels turn
When the machine outgrows the road
Excavators, loaders, dozer transports, modular buildings, bridge stringers — at some point Island Park dirt work puts something on a trailer that the road was not drawn to hold. Idaho draws the line in a statute and a state rule, and crossing it without paper is expensive in a way few contractors appreciate until the scale house does the math. The whole system reduces to one sentence: over the legal box, you carry an ITD special permit before the wheels turn.
The legal box
Title 49 sizes the box every vehicle must fit:
| Dimension | Idaho legal maximum |
|---|---|
| Width | 8 1/2 feet, including the load |
| Height | 14 feet, including the load |
| Length, single motor vehicle | 45 feet |
| Length, trailer or semitrailer | 48 feet (53 on national-network routes) |
| Length, vehicle combination | 75 feet |
| Overhang | 4 feet front / 10 feet rear |
Two exceptions matter on rural equipment moves: the size limits do not apply to farm tractors and implements of husbandry incidentally operated between farm operations in daylight — but any farm tractor hauled on the interstate is capped at 9 feet wide, and a wide implement in transit needs one red or fluorescent orange flag at least 18 by 18 inches on its outermost left projection. A lowboy with an 11-foot-wide excavator is not farm equipment: it is over-width, full stop.
The legal weights
Weight law runs on axle, wheel, and gross numbers, stated in one sentence:
“The maximum single axle gross weight shall be twenty thousand (20,000) pounds, the maximum single wheel gross weight shall be ten thousand (10,000) pounds and the maximum gross vehicle or combination weight shall be one hundred five thousand five hundred (105,500) pounds, provided that maximum gross vehicle or combination weight on United States federal interstate and defense highways of this state shall not exceed eighty thousand (80,000) pounds, except as permitted under the provisions of section 49-1004, Idaho Code.”
— Idaho Code § 49-1001(1). Retrieved 5 October 2026
Axle groups run on a federal bridge-formula table the statute carries in smaller print — and overweight permits hang off the same section. The practical takeaway for a heavy haul: 105,500 pounds is the ceiling on Idaho highways, 80,000 on the interstate, and both bend only with a permit.
The permit rule: a number before the wheels turn
What makes Idaho’s system unforgiving is that the permit must exist before the move starts:
“The owner or operator of an overweight or oversize vehicle shall obtain a permit or shall establish intent to obtain a permit by contacting a permit office and receiving a permit number before moving the vehicle on the highways.”
— Idaho Code § 49-1004(1)(b). Retrieved 5 October 2026
The permit itself may be “in either hard copy or digital format” — but whichever form it takes, it rides in the truck:
“All special permits or evidence of intent to obtain a permit, whether in hard copy or digital format, shall be carried in the vehicles to which they refer and shall upon demand be delivered for inspection to any peace officer”
— Idaho Code § 49-1004(1)(c). Retrieved 5 October 2026
No permit number, no move — not “permit applied for,” not “office knows we are coming.” The phone call that yields the number is the legal start line.
What the permit costs
ITD’s fee rule, effective 7-1-24, prices the common categories:
| Permit | Fee |
|---|---|
| Oversize only, single trip | $30 |
| Overweight/oversize or overweight (non-divisible), single trip | $33 |
| Annual divisible loads (incl. up to 129,000 lb extra length/weight authority) | $45 |
| Overweight/oversize non-divisible, annual | $128 |
| Reissuance or transfer | $15 |
Annual permits bought online run $5 less than the listed price. The rule’s stated philosophy is worth quoting on the bid sheet: the cost of processing, issuing, and enforcing special permits “will be borne by such permittees and not by the general traveling public through the expenditure of highway user funds.” Over-dimension hauling is a purchased privilege, priced per trip or per year.
Flags, signs, and lights
The visibility package is not negotiable, and the specs are exact:
- Warning flags on every over-width load and any rear overhang past four feet: minimum 18 inches by 18 inches, red or fluorescent orange.
- OVERSIZE LOAD signs on anything over legal width: minimum 12 inches high by 5 feet wide, 8-inch letters with 1-inch stroke, black on yellow, front and rear.
- Clearance lights at night: amber at the front extremities, red at the rear; overhang lights marking the load’s true width.
A load flagged with a handkerchief and a hand-lettered door sign fails all three at once.
When the permit can be pulled
The same rule carries tripwires that void the paper:
“Single, tandem, tridem, quad, or other axle groups weight is more than fifteen percent (15%) over” … “Gross or bridge weight is more than seven percent (7%) over.”
— IDAPA 39.03.01.108 (revocation grounds), eff. 7-1-24. Retrieved 5 October 2026
Get caught and the permit dies; repeat and you do: disqualification from reapplying runs 30 days after the first violation, six months after the second, one year after the third. A revoked permit mid-move strands the load wherever it sits.
Clocks, weekends, and rush hour
Permits carry time-of-day geography. On red-coded routes, oversize travel runs daylight hours until 2 p.m. Friday, stops for the weekend, and resumes at sunrise Monday. Loads over 13 feet wide are additionally barred in heavy commuter windows — locally, that includes the Idaho Falls stretch of I-15. Loads over 16 feet wide (16 feet on the interstate is 18) or 120 feet long need extra department approval, which may require up to 24 working hours — and over-height moves run on the same 24-working-hour route evaluation, because someone has to check every bridge and signal on the route. A load 16 feet 6 inches or taller must also contact the local utility companies about power lines before it rolls.
When the load needs an entourage
Beyond the signs come people. Pilot and escort vehicles are furnished by the permittee whenever the permit requires them, and the rule is picky about the escort itself:
- Passenger car or truck, not exceeding 16,000 pounds, and no vehicles towing trailers qualify.
- Loads over 16 feet high lead with a non-metallic height pole deployed.
- Roof-mounted OVERSIZE LOAD sign, flashing amber lights, and headlights on through the movement.
- Two-way radios in both vehicles, reliable over at least a half mile.
- Mandatory kit: STOP/SLOW paddle, three reflective triangles, a five-pound BC fire extinguisher, ANSI Class 2/3 vest, spare signs, hard hat, flashlight, first aid kit.
Truly big loads trigger more than escorts: on two-lane highways, anything over 18 feet wide, 150 feet long, or 16 feet high requires a traffic control plan prepared by a licensed engineer or an ATSSA-certified traffic control supervisor, naming the pullout locations, escort usage, railroad crossings, and the procedure for letting emergency vehicles past.
Break a bridge, buy the bridge
The cost rule outlives the permit:
“The owner and the operator, driver or mover of any vehicle, object or contrivance over a highway or bridge, shall be jointly and severally responsible for all damages which the highway or bridge may sustain as the result of illegally operating or driving or moving any vehicle, object or contrivance, or as the result of driving or moving any vehicle, object or contrivance weighing in excess of the maximum weight specified in this chapter, but authorized by a temporary permit.”
— Idaho Code § 49-1006(1). Retrieved 5 October 2026
Read the second half carefully: damage responsibility attaches even to permitted over-weight moves. And on any bridge with a 19-foot-or-longer span posted for single-lane traffic, only one heavy vehicle at a time may be on it. County bridges on the way to a basin job site are exactly where this bites.
The penalty ladder
Running overweight without paper climbs a statutory ladder that turns steep fast:
| Amount overweight | Penalty |
|---|---|
| 1–1,000 lb | $5 |
| 1,001–2,000 lb | $15 |
| 2,001–4,000 lb | $25 |
| 4,001–15,000 lb | $25 + $0.1341 per pound over 4,000 |
| 15,001–20,000 lb | $1,500 + $0.20 per pound over 15,000 |
| Over 20,000 lb | $2,500 + $0.30 per pound over 20,000 |
At 20,000 pounds over — an easy thing to do with a loaded lowboy — the fine starts at $2,500 and adds thirty cents for every pound past 20,000. The $33 permit was cheaper.
How you actually get one
Three doors, all of them fast:
- Online: ITD’s Permits4Idaho (ITRPS) portal issues permits electronically — this is where the $5 online discount on annual permits comes from.
- By phone: DMV Commercial Vehicle Services, (208) 872-3163, can issue the permit number on the call — the number is what the statute demands before the move.
- In person: Ports of Entry check the paperwork on the road; the nearest to Island Park freight lanes is Sage Junction, eight miles north of Roberts on I-15.
- Measure first: width, height, length, overhang, and axle weights, then match the load against the 8 1/2-foot / 14-foot / 75-foot box before the trailer is loaded.
- Route the move: over-height needs the 24-working-hour route evaluation, tall loads need the utility call, and big loads need the traffic control plan.
- Or hire the move out: a hauler who already carries annual permits and escorts is often cheaper than one expensive lesson. For machines that dig rather than ride: (208) 932-1140.
Related pages: why spring breakup cuts weight limits on the roads themselves, the OSHA rules that follow the machine once it rolls off the trailer, and the ITD approach permit for the driveway the loaded truck turns into.
Common questions
How wide can a load be in Idaho without a permit?
8 1/2 feet, including the load. Height caps at 14 feet, a single motor vehicle at 45 feet, a trailer or semitrailer at 48 feet (53 on national-network routes), and a combination at 75 feet, with overhang limited to 4 feet front and 10 feet rear. Past any of those, it takes an ITD special permit.
How much does an oversize permit cost in Idaho?
Per the state fee rule effective July 1, 2024: $30 for an oversize-only single trip, $33 for an overweight or overweight/oversize non-divisible single trip, $45 for annual divisible-load authority, and $128 for an annual non-divisible permit. Reissuance is $15, and annual permits bought online are $5 less.
When do I need the permit number - before or during the move?
Before. Idaho Code 49-1004 requires the owner or operator to obtain the permit or establish intent by contacting a permit office and receiving a permit number before moving the vehicle on the highways. The permit or evidence of intent, hard copy or digital, must be carried in the vehicle and shown on demand.
What is the maximum legal weight in Idaho?
20,000 pounds on any single axle, 10,000 pounds on any single wheel, and 105,500 pounds gross for a vehicle or combination - dropping to 80,000 pounds on interstate highways except as permitted. Axle groups also run on the federal bridge formula; heavier moves need the overweight permit.
What flags and signs does an oversize load need?
Warning flags at least 18 by 18 inches, red or fluorescent orange, on all over-width loads and on rear overhang past four feet; OVERSIZE LOAD signs at least 12 inches by 5 feet with 8-inch black letters on yellow front and rear; and amber-front, red-rear clearance lights at night.
When does an oversize load need a pilot car in Idaho?
Whenever the permit says so - single-trip permits state it in the escort or restriction section, and annual permit holders follow the state's Pilot/Escort Vehicle Travel map by size and route. Escort vehicles cannot exceed 16,000 pounds, cannot tow trailers, and loads over 16 feet high need a height pole leading them.
Can oversize loads travel at night or on weekends?
Generally no on restricted routes: red-coded routes allow daylight travel only until 2 p.m. Friday, with no weekend movement until sunrise Monday. Loads over 12 feet wide, 120 feet long, or 15 feet high face route-specific limits, and loads over 13 feet wide are barred in commuter windows like the Idaho Falls stretch of I-15.
What happens if the permit weight is exceeded?
The permit can be revoked when an axle group is more than 15 percent over or gross or bridge weight is more than 7 percent over - and repeat violations bar reapplication for 30 days, then six months, then a year. Criminal penalties stack separately under the 49-1013 ladder.
What are the fines for driving overweight without a permit?
They scale with the excess: $5 up to 1,000 pounds, $25 from 2,001 to 4,000, then $25 plus 13.41 cents per pound to 15,000, $1,500 plus 20 cents per pound to 20,000, and $2,500 plus 30 cents per pound beyond that. Twenty thousand pounds over starts the math at $2,500 before the per-pound addition.
Who pays if an oversize load damages a road or bridge?
The owner and the operator are jointly and severally responsible for all damage a highway or bridge sustains - both from illegal operation and from damage caused by permitted over-weight moves. On posted single-lane bridges with spans of 19 feet or more, only one heavy vehicle may cross at a time.
How do I get an Idaho oversize permit?
Three ways: online through ITD's Permits4Idaho portal, by phone from DMV Commercial Vehicle Services at (208) 872-3163 - the number they issue satisfies the before-moving rule - or through Ports of Entry like Sage Junction north of Roberts on I-15. Over-height and extra-wide loads need extra lead time for route review.