Iowa OS/OD Overview
Permit Required
Yes – all oversize or overweight loads require a permit from the Iowa Department of Transportation (Iowa DOT).
Legal Limits (Without Permit)
- Width: 8'6"
- Height: 13'6"
- Length: 70' (combo); 53' max trailer
- Weight: 80,000 lbs GVW (with axle limits)
Permitted Load Maximums (Typical Upper Limits)
- Width: Up to 18' on a routine permit; the first escort comes at over 12'0", not 14'6"
- Height: Over 14'6" requires a front escort with a height pole; the chart's height band runs to 20'
- Length: Over 120' permitted with review
- Weight: Over 156,000 lbs allowed with proper axle spacing and engineering review
Superloads require engineering analysis and coordination with bridge division.
Travel Hours
- Continuous (24/7): permitted loads up to 100' long, 11' wide and 14'6" high, within permitted axle limits, on a roadway at least 22 feet wide with lanes at least 11 feet wide and the safety lighting called for on the Iowa provisions sheet
- Daylight only: anything over 11' wide, over 100' long or over 14'6" high – ½ hour before sunrise to ½ hour after sunset, Saturdays and Sundays included
- Des Moines: I-235 is closed to permitted loads 7:00–9:00 A.M. and 4:00–6:00 P.M. Monday through Friday
- Holidays: holiday restrictions come on the permit's provisions sheet – I do not have a verified Iowa holiday rule, so read the sheet rather than assuming the usual six
Escort Requirements (761 IAC 511.20)
| Dimension | Escort Requirement |
|---|---|
| Width over 12'0" up to and including 14'6" | 1 escort – front on a 2-lane road, rear on a 4-lane road. Either may be replaced by an amber or strobe light on the power unit and on the rear extremity of the vehicle or load (the chart's asterisk) |
| Width over 14'6" up to and including 16'6" | Still 1 escort – front on a 2-lane road, rear on a 4-lane road. The asterisk sits only on the 4-lane cell, so the 4-lane rear escort may be swapped for the amber/strobe lights; the 2-lane front escort may not |
| Width over 16'6" | Not established on this page – the chart bands I verified stop at 16'6". Do not assume the band below carries upward; read it off the permit or ask the Iowa DOT permit office |
| Height over 14'6" up to and including 20' | Front escort with a height pole, on both 2-lane and 4-lane roads. No asterisk on this row, so there is no light substitution |
| Length over 85' up to and including 120' | Warning lights, no escort |
| Length over 120' | Rear escort, on both 2-lane and 4-lane roads |
Every row of the chart reads “over X up to and including Y,” so the bottom of a band never triggers and the top does: a load measuring exactly 12'0" wide needs no escort, one at 12'1" does. Source: 761 IAC 511.20(2), “Minimum Warning Devices and Escort Requirements” (IAC 6/10/26).
Additional Notes
- “Oversize Load” signs, red/orange flags, and amber beacon lights are required
- Iowa DOT uses the AUTOMATE system for permit applications
- Special bridge restrictions and detours are common in rural and flood-prone areas
Detailed Information
PERMITS: Permits valid for five days. Must obtain permit before entering state.
OPERATING TIME: Permitted vehicles up to 100' in length, 11' width, 14'6” height and permitted axle limits may have continuous travel seven days a week (24/7), provided travel is on roadway with a minimum width of 22 feet and minimum lane width of 11 feet, and with safety lighting as specified on Iowa provisions sheet. Larger loads may travel one-half hour before sunrise to one-half hour after sunset, including Saturdays and Sundays.
RESTRICTED TRAVEL: Des Moines I-235 travel prohibited from 7:00 – 9:00 A.M. and from 4:00 – 6:00 P.M. Monday through Friday. Other highways in Des Moines can be included under the curfew at officer’s discretion if traffic is heavy.
LEGAL DIMENSIONS: Width: 8'6" Height: 13'6" Length: 53' semi-trailer and load. (Overhang which results in over 53' semi- trailer and load length is not legal without permit. Steel pipe, beams and constructions materials aren’t exempt.) Weight: 80,000 Gross Single – 20,000 Tandem – 34,000 Tridem – 42,000 (w/ minimum 8'1" axle spacing)
ROUTINE PERMIT LIMITS: Width: 18' Height: 18' Length: 120' Weight: Single – 20,000 Tandem – 46,000 Tridem – 60,000 Quad-80,000 Steer Tire: Permit does not break out the steer axle weight but enforcement goes by the single (steer) tire weight rating (on the side of the tire) times two. You must be licensed for as much as you wish to permit in Iowa. Loads exceeding these dimensions or weight are considered as super loads.
ESCORTS: Read straight off the escort chart at 761 IAC 511.20(2). Width over 12'0" up to and including 14'6" – one escort: front on a 2-lane road, rear on a 4-lane road. Both cells in this band carry the asterisk, and the asterisk is the whole job: “In lieu of an escort, a carrier can display an amber light or strobe light on the power unit and on the rear extremity of the vehicle or load.” A carrier who lights the load owes you nothing in this band. Width over 14'6" up to and including 16'6" – still one escort, same split: front on a 2-lane road, rear on a 4-lane road. Here the asterisk sits only on the 4-lane cell, so on a 4-lane the rear escort can still be traded for the amber/strobe lights, but on a 2-lane the front escort is not optional. Width over 16'6" – I am not printing a figure. The bands I verified stop at 16'6"; get the requirement above that from your permit or the Iowa DOT permit office. Height over 14'6" up to and including 20' – a front escort with a height pole, on both 2-lane and 4-lane roads. That row carries no asterisk, so lights do not buy out of it, and the pole is standard kit for any Iowa front escort anyway: “A pole used for measuring vertical clearances is mounted on the front escorting vehicle” (511.20(1)(j)). Length over 85' up to and including 120' – warning lights, no escort. Length over 120' – a rear escort, on both 2-lane and 4-lane roads. Two corrections worth naming, because the wrong version is on a lot of sites and was on this page until now: Iowa's first escort is at over 12'0", not over 14'6", and there is no front-and-rear pair at 16' – above 14'6" Iowa still asks for one escort, not two. On overhang: the front-projection and rear-overhang figures in the SIGNS, FLAGS & LIGHTS note below are lighting triggers. I did not re-verify a projection row in the escort chart, so treat any escort-for-overhang claim as unconfirmed and take it from the permit.
MISCELLANEOUS: Blades, buckets, counterweights, etc. do not have to be removed when the load is just over dimension. If the load is overweight, they must be hauled separately.
SIGNS, FLAGS & LIGHTS: "Oversize Load" signs and flags are required when a vehicle and load exceeds 75' in length, 8'6 width, and/or 14'4 in height. Flags are required for rear overhang exceeding 4 feet on all permitted vehicles/ loads. Flags should be mounted at each front corner of the towing unit, at each rear corner of the load, and at any wide points/protrusions of the load. An amber revolving light at least 7" high and 7" in diameter is required on the towing unit whenever length exceeds 85', front overhang exceeds 25' or rear overhang exceeds 10' (light should be on the load in the rear) or weight exceeds 80,000 lbs. An escort can be used in lieu of amber light.
