Montana truck chain law
From October 1 through April 30, trucks of 26,001 lb GVW or more towing a trailer must carry approved traction devices in designated chain areas. $225 fine for a first offense.
| Type | Must carry chains (dated or standing rule) |
|---|---|
| Carry season / effective dates | October 1 through April 30 (MCA 61-9-436). Chains can be required year-round when MDT posts them (MCA 61-9-406). |
| Who must carry chains | Motor trucks 26,001 lb GVW or greater towing a trailer, on designated mountain passes. Four-wheel-drive vehicles are exempt from the carry rule. |
| When you must chain up | When MDT posts chains required, all vehicles towing a trailer must chain the drive wheels of one axle. AutoSocks are an approved alternative (MDT). |
| Where | 29 designated areas, including I-90 Lookout, Homestake and Bozeman passes, I-15 Elk Park and Boulder hills, US 2 Marias Pass, US 12 MacDonald Pass (full list on MDT page). |
| Penalty | Failing to carry: $225 for a first offense; $225 to $500 for later offenses (MCA 61-9-436(2)). Penalty for not chaining when posted: Not stated in the official sources we checked. Confirm with the state. |
| Law | MCA 61-9-406; MCA 61-9-436 |
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 Montana IFTA rates.