Studded tires and the mountain traction law in Colorado

The stud allowance sits inside a general prohibition. Section 42-4-228 (3) bars any block, stud, flange, cleat or spike of a material other than rubber from projecting beyond the tread, and then carves out three exceptions: studs of no more than one-sixteenth of an inch on light single-tired vehicles, farm machinery whose protuberances will not injure the highway, and tire chains of reasonable proportions on any vehicle when snow or ice makes them necessary for safety. The three-fourths-ton ceiling and the single-tire requirement mean a dually pickup or a loaded commercial truck gets no stud exception at all. This language has not been touched since Title 42 was recodified effective January 1, 1995, and nothing anywhere in Title 42 sets an installation or removal date, which is why Colorado shops fit studs in October and drivers in Leadville or Steamboat Springs can legally leave them on through July.

The same section carries Colorado's tread-depth floor. Under 42-4-228 (5)(c)(III) a tire is unsafe if tread depth measures less than two thirty-seconds of an inch in any two tread grooves at three locations equally spaced around the circumference, or if the wear indicators contact the road at those points, with commercial vehicles as defined in section 42-4-235 (1)(a) excluded from that subparagraph. The executive director of the Department of Revenue writes the visual-inspection and gauge-measurement rules officers use, under 42-4-228 (5)(b).

The traction law is a separate machine. C.R.S. § 42-4-106 (5)(a)(I)(B) lets the Colorado Department of Transportation restrict a state highway when icy or snow-packed conditions exist unless the vehicle carries tire chains or an alternate traction device, or has four-wheel drive with tires of at least three-sixteenths of an inch tread that are imprinted with a mountain-snowflake, "M&S", "M+S" or "M/S" symbol or are all-weather rated, or the same on all-wheel drive. Senate Bill 25-069, effective August 6, 2025, rewrote that list. A two-wheel-drive car no longer qualifies on winter tires alone: for a front-wheel-drive sedan the only compliant options are chains or a device on CDOT's approved list, which currently names Alpha Trax and EasySox cable chains, the AutoSock and the ISSE Tire Sock. Section 42-4-106 (5)(c)(I) defines an alternate traction device as one CDOT approves as giving traction comparable to metal chains, and (5)(c)(III) defines tire chains as metal chains with at least nine evenly spaced cross chains.

Two seasonal windows run automatically rather than waiting for a storm. Subsection (5)(a)(I)(C.5), added by Senate Bill 24-100 and effective August 7, 2024, applies the equipment requirement to any motor vehicle on I-70 from Dotsero to Morrison for the whole of September 1 through May 31. Subsection (5)(a)(I)(C) does the same across the western slope for commercial vehicles with a declared gross vehicle weight rating of 16,001 pounds or more, on I-70 west of milepost 259 (Morrison), Colorado 9 from milepost 63 to 97 (Frisco to Fairplay), US 40 west of milepost 256 (Empire), US 50 west of milepost 225 (Salida), US 160 west of milepost 304 (Walsenburg), US 285 west of milepost 250 (Morrison), and all of US 550 from milepost 0 to 130. Anywhere else, the restriction bites once CDOT erects signs, including temporary or electronic signs. CDOT publishes active restrictions on COtrip.org and treats the passenger vehicle chain law, under which every vehicle must actually be running chains or an approved device, as the last step before it closes the road under 42-4-106 (5)(a)(I)(A).

A stud or tire-equipment violation under 42-4-228 (1), (2), (3), (5) or (6) is a class A traffic infraction, carried on the penalty schedule at 42-4-1701 (4)(a)(I)(D) at a $15 penalty plus a $6 surcharge. Selling a vehicle for highway use with tires that fail subsections (5) and (6) is heavier: 42-4-228 (8)(b) makes that a class 2 misdemeanor traffic offense, punishable under 42-4-1701 (3)(a)(II)(A) by ten to ninety days imprisonment, or a fine of $150 to $300, or both.

Traction law penalties are set out at 42-4-1701 (4)(a)(I)(F) and are much larger. Proceeding without the required equipment costs $100 plus a $32 surcharge. If the violation causes an incident that closes a travel lane in either direction, it is $500 plus a $156 surcharge. A commercial vehicle violation runs $500 plus $78, and a commercial violation that closes a lane runs $1,000 plus $156. Under 42-4-106 (5)(a)(V) the enhanced portion of a commercial fine is routed to the state treasurer for the highway construction workers' safety account within the highway users tax fund. Section 42-4-106 (5)(a)(VI) exempts a tow operator towing a vehicle, or driving to a vehicle it will tow, from the commercial enhancements. Enforcement is shared: CDOT imposes and signs the restriction and the Colorado State Patrol is directed by 42-4-106 (5)(a)(I)(D) to cooperate in enforcing it. Note also that House Bill 26-1076, signed May 29, 2026 and effective August 12, 2026, changed how many drive wheels a commercial driver must chain, moving that from the statute to CDOT's chain law and passenger vehicle traction law rules, and dropped tire cables from the comparison used to define an alternate traction device.