Idaho truck chain law
On Lookout Pass and Fourth of July Pass (I-90) and Lolo Pass (US 12), ITD can require chains on commercial vehicles when conditions are unsafe, never on bare pavement.
| Type | Chain up when posted |
|---|---|
| Carry season / effective dates | None in statute; ITD may set the requirement "at any time" conditions are unsafe (Idaho Code 49-948(5)). |
| Who must carry chains | Not stated in the official sources we checked. Confirm with the state. |
| When you must chain up | When ITD posts the requirement: chain at least one tire on each side of one drive axle and one axle at or near the rear of each towed vehicle (not a variable-load axle or converter dolly). Equivalent traction devices are allowed. Exemptions include school buses, farm, agricultural, forest-product, mine-product, U.S. mail and tow trucks (49-948(9)). |
| Where | I-90 Lookout Pass and Fourth of July Pass; US 12 Lolo Pass. |
| Penalty | Not stated in the official sources we checked. Confirm with the state. |
| Law | Idaho Code 49-948(5)–(9) |
Official sources
Checked 2026-10-29. Chain controls are set live by the state, so follow posted signs and officers. Not legal advice.
Running the mountains this winter? Estimate fuel tax with the IFTA calculator and see Idaho IFTA rates.