Idaho Tire Chain Laws

How Idaho handles chains

A chain-up violation is an infraction under Idaho Code 49-236(2), and 49-948 has no penalty clause. The Idaho Supreme Court's infraction penalty schedule has no 49-948 line. Its catch-all totals are $67 non-moving or $90 moving, fixed penalty plus court costs, and it does not say which applies. There is no chain season. The order covers three passes: Lookout and Fourth of July on I-90, and Lolo on US 12. It binds commercial vehicles over 26,000 pounds. Chain one tire each side of one drive axle. Watch Idaho 511.

When, where, and what counts

• When required: No fixed chain season. The October 1 to April 30 window is for studded tires, not chains. ITD activates chain-up only when a covered pass is unsafe, with advance signs and a safe pull-out point before the chain-up line.
• Where: The three passes named in the statute: Lookout Pass and Fourth of July Pass on I-90, and Lolo Pass on US 12.
• Applies to: Commercial vehicles rated over 26,000 pounds. Idaho Code 49-948(5) uses only the two weight tests of the commercial vehicle definition in Idaho Code 49-123(2)(d): a gross vehicle weight rating over 26,000 pounds, whatever the unit tows, or a gross combination weight rating over 26,000 pounds that includes a towed unit rated over 10,000 pounds. A vehicle built to carry 16 or more people, or a placarded hazmat vehicle, is not covered unless it also meets one of those weight tests. Exempt under Idaho Code 49-948(9): ITD vehicles maintaining the interstate or state highway system, school vehicles that carry only students and teachers when the school owns and runs them, or leases or contracts them and uses them for no other commercial work, farmers hauling their own farm equipment or supplies to the farm, agricultural product haulers, vehicles carrying only US mail or US property, forest product carriers including chip trucks, mine product carriers including sand, gravel and aggregates but not petroleum products, and wreckers and tow trucks.
• Chains vs traction devices: Chain a minimum of one tire on each side of one drive axle, whatever the number of drive axles, plus one axle at or near the rear of each towed vehicle. That rear axle cannot be a variable load suspension axle or an axle of a converter dolly. Chains go on in addition to pneumatic tires, so snow tires do not substitute. Idaho defines chains as metal traction devices with two circular metal loops, one on each side of the tire, joined by at least nine evenly spaced chains across the tread (Idaho Code 49-104(5)). The statute does allow a substitute for chains themselves: any other traction device differing in construction, material or design but capable of providing traction equal to or exceeding that of chains under similar conditions (Idaho Code 49-948(6) and (7)). Idaho publishes no approved product list, so a device like AutoSock stands on that equivalence test rather than on a state approval.
• Check the live order: Idaho 511 (511.idaho.gov), including its live truck restrictions list (511.idaho.gov/list/truckrestrictions), for the active pass order; watch the advance chain-up signs before Lookout, Fourth of July, and Lolo passes.
• Fine: Idaho Code 49-948 sets no chain-specific fine. Violating the posted chain-up order is an infraction under Idaho Code 49-236(2). You pay a fixed penalty plus court costs from the Idaho Supreme Court's Infraction Penalty Schedule (Idaho Infraction Rule 9(b)), and no court can withhold judgment or suspend any part of it (Idaho Infraction Rule 9(d)). The schedule effective July 1, 2025 has no line for 49-948. Its catch-all lines are $67.00 total for other non-moving violations ($10.50 penalty plus court costs) and $90.00 total for other moving violations ($33.50 penalty plus court costs). The schedule does not say which one a chain-up citation falls under. Confirm the current figure with ITD or the court before you rely on a number.

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