Montana Oversize & Overweight Permit Rules
What a load can be in Montana without a permit, where the permit and escort tiers start on non-interstate and interstate, when it can move, and who to call. Every figure is the JaloPermit Atlas entry for Montana, shown as the app shows it.
Rules as of Jul 31, 2026 · Links checked Jul 13, 2026
Read this before you trust a number. Rules change. The issued permit, posted signs and the state permit office always win over this page. JaloPermit is a reading aid, not a permit-filing service. Guests get 3 free decodes a day with no account and no card, logged-in users get 10 a day, and extra decodes are $3.50 each with no subscription.
What moves in Montana without a permit
Legal limits are the dimensions and gross weight a vehicle may run at without an oversize or overweight permit. Montana publishes its length limit as overall combination, so compare it against that measurement on your permit, not the overall rig.
Where the permit and escort tiers start
| Dimension | Legal without permit | Permit tier starts | First escort on non-interstate | First escort on interstate |
|---|---|---|---|---|
| Width | 8'6" | 8'7" | 12'7" · Front escort | 16'7" · Rear escort |
| Height | 14'0" | 14'1" | 17'1" · Front + High pole | 17'1" · Front + High pole |
| Length | 75'0"overall combination | 75'1" | 150'1" · Rear escort | No escort tier (permit only) |
| Weight | 80,000 lbs | 80,001 lbs | No escort tier (permit only) | No escort tier (permit only) |
"Permit tier starts" is the lowest size in the Atlas ladder that needs a permit. "First escort" is the lowest size that adds a private or police escort on that road class; the full ladder with each tier's rule and source is below.
Montana escort ladder, tier by tier
Open a tier to read the rule behind it, quoted with its source. Amber tiers add a police escort or a superload review; grey tiers are permit-only with conditions.
On non-interstate
Escorts begin at 12'7" wide
Width
Permit required8'7" – 12'6"
Permit required; no pilot vehicle up to 12 ft 6 in wide
Front escort12'7" – 16'6"
Over 12 ft 6 in to 16 ft 6 in: one front pilot vehicle. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Front + Rear16'7" – 18'
Over 16 ft 6 in to 18 ft: one front and one rear pilot vehicle. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Front + Rear18'1" – 24'
Over 18 ft to 24 ft: at least two front and one rear pilot vehicle. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Front + Rear24'1"+
Over 24 ft: at least two front and two rear pilot vehicles. Above 40 ft, this row's escorts are the minimum; the permit sets any more. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Height
Permit required14'1" – 17'
Permit required; no pilot vehicle up to 17 ft high
Front + High pole17'1" – 24'
Over 17 ft to 24 ft: one front pilot vehicle with height pole or equivalent overhead detection. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Front + High pole + Rear24'1"+
Over 24 ft: one front pilot with height pole plus one rear pilot. Above 40 ft, this row's escorts are the minimum; the permit sets any more. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Length
Permit required75'1" – 150'
Permit required; no pilot vehicle up to 150 ft long
Rear escort150'1" – 200'
Over 150 ft: one rear pilot vehicle. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Front + Rear200'1"+
Over 200 ft: one front and one rear pilot vehicle. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Weight
Permit required80,001 lbs+
No pilot vehicle for weight alone. Montana requires pilot vehicles for an overweight load only when the permit lists a bridge restriction (ARM 18.8.602(2)): a 10 mph crossing in the driving lane needs at least one rear pilot vehicle; a 10 mph crossing centered on the bridge needs two, one front and one rear off the Interstate (two rear on the Interstate). MDT prints these as permit restrictions 17a/17b (centerline) and 18a/18b (slowdown), so the permit's restrictions decide. Source: ARM 18.8.602(2) (amended 8/29/2020); ARM 18.8.511A(5); MDT eTRIPs Permit Restrictions (updated 07/27/2026).
On interstate
Escorts begin at 16'7" wide
Width
Permit required8'7" – 16'6"
Permit required; no pilot vehicle on interstate up to 16 ft 6 in wide
Rear escort16'7" – 18'
Over 16 ft 6 in to 18 ft: one rear pilot vehicle. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Rear escort18'1"+
Over 18 ft: at least two rear pilot vehicles side by side; superload approval also required. Above 40 ft, this row's escorts are the minimum; the permit sets any more. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Height
Permit required14'1" – 17'
Permit required; no pilot vehicle up to 17 ft high
Front + High pole17'1" – 24'
Over 17 ft to 24 ft: one front pilot vehicle with height pole or equivalent overhead detection. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Front + High pole + Rear24'1"+
Over 24 ft: one front pilot with height pole plus one rear pilot. Above 40 ft, this row's escorts are the minimum; the permit sets any more. When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
Length
Permit required75'1"+
Permit required; Montana sets no length-triggered pilot vehicle requirement on the interstate
Weight
Permit required80,001 lbs+
No pilot vehicles required for weight on the interstate unless the permit adds restrictions
When more than one size needs an escort
When a load meets more than one pilot-vehicle rule, the rule needing the most pilot vehicles sets the number (ARM 18.8.511A(2)); a load over 17 ft high keeps its front pilot with the height pole, and the permit's numbered restrictions place the rest.
When a permitted load can move
- Standard hours
Interstate: 24/7 up to 18' wide. Non-interstate: 24/7 up to 10' wide, 150' long, 15'6" high; above any of those, daylight only. Overweight loads under a Bridge Centerline condition are daylight only unless otherwise authorized. The conditions printed on your permit control.
- Night travel
Permitted. Interstate: allowed up to 18' wide. Non-interstate: up to 10' wide, 150' long, 15'6" high; above any of those, daylight only. Full length and width must be lighted per 49 CFR 393.11. Overweight loads on a Bridge Centerline condition are daylight only.
- Weekend travel
Non-interstate: loads exceeding 18' wide, 150' long or 17' high are not allowed weekend travel. Below those sizes there is no weekend curfew; interstate travel stays 24/7 up to 18' wide. Holiday weekends are more restrictive - see holiday restrictions.
- Holiday restrictions
Holidays: New Year's, Memorial Day, July 4, Labor Day, Thanksgiving, Christmas, plus adjacent weekend days. Interstate: 24/7 to 18' wide; over 18' no travel. Non-interstate: 24/7 to 10'/150'/15'6"; over 10' to 12'6" wide daylight only; over 12'6" wide, 150' or 15'6" no travel.
- Urban restrictions
No urban curfews statewide. Two permanent corridor limits: MT-35 Polson-Bigfork is closed to loads over 9' wide unless the origin or destination is between them; US-87 Belt-Raynesford is limited to 12'6" wide, with a permanent detour via US-89 and S-427.
Signage Montana expects
- Oversize load sign
Required on loads exceeding 10' wide. An OVERSIZE LOAD sign must be mounted at any visible height on the front and rear of the load, letters at least 8 inches high, black on a yellow background. Signs must be removed when the move is complete.
- Flags
Standard flags at extremities
- Beacons
Required on loads exceeding 10' wide. Flashing amber lights at least 5 inches in diameter, 50 candlepower, 60 to 90 flashes per minute, mounted on the power unit at each end of the oversize load sign and visible 360 degrees. Revolving or strobe lights may substitute.
Montana permit office
The permit office is the authority on every number on this page. Call it, or open the official site, before you rely on a threshold for a load that is close to a line.
Already have your permit?
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What are the legal limits in Montana without an oversize or overweight permit?
In Montana, the legal limits without an oversize or overweight permit are 8'6" wide, 14'0" high, 75'0" long (overall combination) and 80,000 lbs gross. Legal overhang is 3'0" front and 4'0" rear. Anything over those figures needs a permit from the Montana permit office before it moves.
When does an oversize load need an escort or pilot car in Montana?
On non-interstate in Montana, escorts begin at 12'7" wide. On interstate, escorts begin at 16'7" wide. The first escort tier is "Front escort" at 12'7" – 16'6" wide. Every tier on this page quotes its rule and source.
Can oversize loads travel at night, on weekends or on holidays in Montana?
Night travel: Permitted. Interstate: allowed up to 18' wide. Non-interstate: up to 10' wide, 150' long, 15'6" high; above any of those, daylight only. Full length and width must be lighted per 49 CFR 393.11. Overweight loads on a Bridge Centerline condition are daylight only. Weekend travel: Non-interstate: loads exceeding 18' wide, 150' long or 17' high are not allowed weekend travel. Below those sizes there is no weekend curfew; interstate travel stays 24/7 up to 18' wide. Holiday weekends are more restrictive - see holiday restrictions. Holidays: Holidays: New Year's, Memorial Day, July 4, Labor Day, Thanksgiving, Christmas, plus adjacent weekend days. Interstate: 24/7 to 18' wide; over 18' no travel. Non-interstate: 24/7 to 10'/150'/15'6"; over 10' to 12'6" wide daylight only; over 12'6" wide, 150' or 15'6" no travel.