Illinois OS/OD Overview
Permit Required
Yes – any load exceeding legal size or weight must have a permit from the Illinois Department of Transportation (IDOT). Single-trip and term permits are issued through IDOT's ITAP (Illinois Transportation Automated Permits) system.
Legal Limits (Without Permit)
- Width: 8'6"
- Height: 13'6"
- Length: 75' (combo); 53' trailer allowed
- Weight: 80,000 lbs GVW (standard axle limits apply)
Anything over a legal dimension or weight requires an oversize/overweight permit before the move. Superloads beyond routine permit limits require engineering review, route survey, and possible bridge analysis.
Travel Hours
- Standard: Loads over 14'6" wide travel Monday–Friday sunrise to sunset, and Saturday sunrise until noon.
- Holidays: No travel on New Year's Day, Memorial Day, July 4, Labor Day, Thanksgiving, or Christmas.
- Night travel: Generally not permitted for over-dimensional loads; verify lighting and route conditions on the issued permit.
Escort Requirements (General Guidelines)
| Dimension | Escort Requirement |
|---|---|
| Width > 14'6" | Pilot car – front on 2-lane undivided highways, rear on divided highways |
| Width > 18' | State police escort (all highways) |
| Height > 14'6" | Height-pole vehicle required |
| Height > 18' | State police escort |
| Length > 110' | Rear pilot car |
| Length > 145' | Front pilot car (2-lane highways) |
| Length > 200' | State police escort |
Detailed Information
ESCORTS: State police escort is required for overall lengths over 200', widths over 18', or heights over 18' (92 Ill. Adm. Code 554.204). A front pilot car is required for combinations over 145' overall length on 2-lane highways; a rear pilot car for combinations over 110'. For width over 14'6", a front pilot car is required on 2-lane undivided highways and a rear pilot car on divided highways (92 Ill. Adm. Code 554.208).
HEIGHT POLE: A height-pole vehicle is required when the load exceeds 14'6" in height (92 Ill. Adm. Code 554.208).
RESTRICTED TRAVEL: Loads over 14'6" wide are restricted to daylight hours Monday through Friday and Saturday morning until noon, and may not travel on the six major holidays. Movement through Chicago and other metro areas may carry additional local restrictions noted on the permit.
Additional Notes
- "Oversize Load" signs, red/orange flags, and amber warning lights are required on the load and escort vehicles per IDOT permit conditions.
- The Illinois Tollway and certain structures may carry separate routing or clearance requirements.
- Permit conditions issued by IDOT govern the specific move and may impose requirements beyond these general thresholds.
Source: Illinois DOT — Oversize/Overweight Permits. Informational only — always verify against the live IDOT permit office before any move; permit conditions control.
