Winter driving and chain laws for truck drivers

A chain law is a state rule that requires vehicles to carry or mount tire chains, or an approved traction device, to keep driving in winter conditions. For a heavy truck, a posted chain control usually means chains on now, and some mountain states also require you to carry chains all winter whether or not it is snowing. The details differ by state, so this guide covers technique first, then how California, Colorado and Washington run their systems.

This guide is general information, not legal advice. Chain rules change, so confirm the current requirements with the state DOT or state patrol before you travel.

Winter driving technique

Most winter trouble starts with speed that was fine a mile earlier. Slow down before conditions force you to, and give yourself far more following distance than on dry pavement, because stopping distances grow on snow and ice.

• Keep every input smooth. Gentle throttle, early braking and small steering corrections keep the drive tires and trailer in line.
• Watch bridges, overpasses and shaded curves, which can freeze before the rest of the road.
• Stay off cruise control on slick roads so you control every change in power.
• Keep the windshield, mirrors, lights and reflectors clear at every stop.
• Carry gloves, a headlamp, a high-visibility vest, extra chains and repair links, and practice chaining up in dry weather.

Know when to stop. Caltrans itself notes that when conditions are severe enough to require chains on inside duals, it may be better to postpone the trip. If weather delays you, read how the adverse driving conditions exception works before you count on it.

How chain laws work

Chain laws come in two forms. Carry requirements make you have chains in the truck on certain routes during certain months. Mounting requirements take effect when signs are posted and mean the chains go on the tires before you continue.

States announce chain controls with static and electronic signs, and often set up checkpoints. A truck without chains can be held, turned around, or kept out of the control area entirely. Several states accept approved alternatives, such as textile devices or automatic chains, but each sets its own conditions.

California: R-1, R-2 and R-3

Caltrans uses three chain requirement levels:

The key line for truck drivers is on Caltrans' truck page: when chains are posted, all heavy-duty vehicles over 6,500 pounds gross must have chains mounted to proceed. The R-level mostly changes the exemptions for lighter vehicles.

California has no set dates for carrying chains, but vehicles without chains are not allowed into chain control areas, and there is no parking at the checkpoints. Over Donner Pass on I-80, heavy trucks usually need link-type chain on at least the main drive axle. Caltrans' status codes also include R-1 Modified, for trucks and vehicles pulling trailers, and TS, which means trucks must stop at the checkpoint and carry maximum chains to proceed.

Caltrans lists where chains are most often required: I-5 north of Redding, I-80 over Donner Pass, US 50 over Echo Summit, State Route 58 near Tehachapi, I-15 over Cajon Pass and I-5 over Tejon Pass. Check conditions on Caltrans QuickMap or by calling 800-427-7623.

Colorado: carry season and chain law codes

Colorado requires commercial vehicles over 16,000 pounds used in commerce, and vehicles carrying 16 or more passengers, to carry chains or approved traction devices from September 1 to May 31 on these routes, whatever the weather:

• I-70 west of milepost 259 (Morrison) to the Utah line
• Colorado 9 from milepost 63 to milepost 97 (Frisco to Fairplay)
• US 40 from milepost 256 (Empire) to the Utah line
• US 50 from milepost 225 (Salida) to the Utah line
• US 160 from milepost 304 (Walsenburg) to the New Mexico line
• US 285 from milepost 250 (Morrison) to the New Mexico line
• All of US 550

Combination vehicles must chain four drive tires. Single drive axle combinations can use 4 tire chains, 4 AutoSocks, automatic chains or sanders, with no cables allowed. Tandem drive axle combinations may use cables of at least 0.415 inches only if the outer tires on both ends of one drive axle carry chains and at least four devices are used in total.

CDOT's travel restriction rules number the stages of the chain law. Code 15 is the passenger traction law and Code 16 is the passenger chain law. The commercial stages are Code 17, which requires single drive axle combinations to chain, and Code 18, which requires all commercial vehicles to chain. While any code is in effect, commercial vehicles must stay in the right lane except to pass a stalled or slower vehicle.

The Colorado State Patrol lists the penalty for non-compliance as up to $500 plus a $79 surcharge, rising to $1,000 plus a $157 surcharge if you get stuck and block the road. CDOT announces restrictions on road signs and on COtrip (cotrip.org).

Washington: chains over 10,000 pounds

Washington's rule, WAC 204-24-050, requires vehicles over 10,000 pounds GVWR to carry enough chains from November 1 to April 1 on listed routes. These include I-90 between North Bend and Ellensburg (Snoqualmie Pass), State Route 2 between Index and Dryden (Stevens Pass), State Route 12 between Packwood and Naches (White Pass), and I-82 between Ellensburg and Selah. Every vehicle over 10,000 pounds GVWR must also carry at least two extra chains.

When signs read "Chains required, vehicles over 10,000 GVWR" or "Chains required on all vehicles except all-wheel drive," chains must be mounted before you enter. The number of chained tires depends on your axle count, and WSDOT publishes a diagram for each configuration. Oversize permit loads are prohibited on mountain passes while these signs, or a traction advisory with oversize vehicles prohibited, are displayed.

Chain-up areas and safe chaining

Chain up only in a designated chain-up area or a pullout fully off the travel lanes. Colorado designates chain stations specifically to give drivers room to install chains.

1. Pull fully off the road, set the brakes and turn on your flashers.
2. Put on your vest and gloves before you step out.
3. Lay out the chains, fit them, and drive a short distance to let them seat.
4. Stop again and retighten.
5. Remove the chains where the signs end the control, and keep your speed down while they are on.

Check conditions and cameras before the pass

Check before you climb, not at the checkpoint. Caltrans QuickMap, COtrip and WSDOT's traveler information show chain controls, closures and conditions, and live DOT cameras let you see the road surface for yourself. National Weather Service alerts tell you what is coming over the next few hours.

How Fort Route helps

Fort Route's traffic cameras include 12,999 live DOT cameras from Caltrans, Oregon's TripCheck, WSDOT, Iowa DOT, Illinois DOT through Travel Midwest, MnDOT, NDDOT and SDDOT. Your route card shows how many live cameras are on your route, with thumbnails, and each camera opens a live image that refreshes every minute. Colorado's cameras aren't included, so use COtrip there.

Fort Route also shows National Weather Service alerts along your route and steep-grade warnings before long downgrades. It doesn't track chain control status, so check the state DOT for the current level before every pass.