Colorado's Chain Law Begins September 1st for Commercial Vehicle Drivers on I-70

August 29, 2011 - Statewide Transportation Plan - STATEWIDE— With the summer quickly coming to a close, the Colorado Department of Transportation (CDOT) is preparing for the first snowfall in the high country and with the chain law season starting in September, commercial vehicle drivers should also be preparing for the winter ahead.

Starting September 1st, all commercial vehicles traveling on I-70 between milepost 133 (Dotsero exit) and milepost 259 (Morrison exit) must carry sufficient chains to be in compliance with the Colorado chain law. The law requires commercial vehicles to carry chains on this segment of I-70 from September 1st to May 31st.

“Colorado’s first snow fall can hit at any moment in the higher elevations and we don’t want commercial vehicle drivers to be caught off guard,” said CDOT Region Transportation Director Tony DeVito.  “To help drivers comply with the chain law, we have 21 chain stations along the I-70 corridor as well as numerous programs that aid drivers with their winter travels.”

Colorado’s chain law applies to all state, federal and Interstate highways and was initially enacted in 1996. It includes two levels for commercial vehicles.

    • Chain Law Level 1 requires all single drive axle combinations commercial vehicles* to chain up.  All four drive wheels must be chained; cables are not permitted as an alternate traction device. All other commercial vehicles must have snow tires or chains. Level 1 may be implemented any time there is snow covering any part of the traveled portion of pavement on an ascending grade.
    • Chain Law Level 2 requires all commercial vehicles to chain up. Auto transports must comply to the extent possible without causing damage to hydraulic lines. Buses must chain two drive wheels to comply.  Level 2 may be implemented any time there is snow covering the entire traveled portion of pavement on an ascending grade or when driving conditions dictate this level is necessary to protect safety and minimize closures.

To help ensure that commercial vehicles have a safe location to chain up or down, CDOT has 21 chain stations along the I-70 west corridor, many of which have been improved over the last several years and provide more parking and a safer environment. Truck drivers are advised to watch for yellow signs indicating exact chain station locations. The 11 chain stations on eastbound I-70 are located at mileposts 178, 183, 184 (shoulder), 187 (shoulder), 195, 203 (scenic area), 205, 219, 228, 241 and 251.  The ten chain stations on westbound I-70 are located at mileposts 263, 260, 254 (Buffalo Overlook), 228, 223, 221, 219, 213 (brake check area) and 197 (scenic area) and 179.

In addition, CDOT has a few chain stations on the I-70 east corridor at mileposts 289 and 343 eastbound and milepost 358 westbound.  There is also a chain station located on northbound I-25 at milepost 157 (near Monument) and southbound at milepost 172 (near Larkspur).

The alternate traction control device known as the AutoSock™ remains an approved device in Colorado.  Commercial vehicles (both single and double axle) exceeding 26,000 Gross Vehicle Weight or vehicles carrying 16 passengers or more will have the option of using AutoSock™ rather than chains.  This traction control device is a fabric that slips over a vehicle’s outer driving wheels, providing extra traction on snowy and icy roads.  It also can be installed over the tire in less time than traditional chains.

To help keep the highways clear and traffic moving, CDOT will continue its heavy tow program for the fifth year in a row.  The program is designed to promptly clear disabled heavy trucks from the highway in order to open the road more quickly.

“Since the inception of the program in 2007, we have greatly reduced traffic delays and congestion due to disabled vehicles,” said CDOT Traffic Engineer Bernie Guevara.  “In fact, last year, nearly 200 commercial vehicles were relocated, 214 lanes were cleared and the average clearance time was approximately 22 minutes.”

Heavy tow coverage will begin around Thanksgiving and will continue each weekend through late March or early April 2012.  Typical hours of operation are Saturdays from 6 a.m. to 2 p.m. on westbound I-70 and Sundays from 2 p.m. to 10 p.m. on eastbound I-70.  Other coverage days include Martin Luther King Jr. Day and President’s Day.  Other days may be added for inclement weather if CDOT deems it necessary.

CDOT also offers one other program to help commercial vehicle driver through inclement weather. The chain assistance program allows vendors to assist commercial vehicles when the Colorado Chain Law is in effect by selling and installing chains and other approved equipment.

Vendors will be on site at chain stations where the chain law is currently in effect.  The service will be available starting around Thanksgiving, depending on weather.

For the safety of the drivers and the traveling public, CDOT strongly encourages drivers to use the chain stations and follow the reduced speed limit which will be displayed at the respective electronic Variable Speed Limit signs near each chain station when the chain law is in effect. In addition, please be cognizant of the right lane restriction for all slow moving vehicles on all uphill grades greater than six percent except when it’s necessary to obey traffic control devices, exit or enter the Interstate or when weather or traffic conditions require otherwise.

Commercial vehicle drivers are also encouraged to sign up for e-mail and text message alerts on chain laws and other road condition information.  To receive updates visit and click on the logo in the upper right-hand corner below the search function and choose the appropriate items under “Chain Law” as well as any other traveler information you may be interested in.

Road condition and chain law information may also be found at or by calling 511.

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*Colorado’s chain law defines commercial vehicles as being used in commerce to transport passengers or property and fitting into one of the following categories:

>Gross combination weight rating of 26,001 or more lbs. inclusive of a towed unit which has a gross vehicle weight ration of more than 10,000 lbs

>Gross vehicle weight rating of 26,001 or more lbs

>Designed to transport 16 or more passengers, including the driver