Colorado-Specific Signs: Mountain and Weather Driving Signage
Colorado's mountains and plains produce signage you will not see at sea level: traction and chain laws, runaway truck ramps, avalanche gates, and wind and snow warnings. This domain tests whether you recognize those signs and act before the hazard rather than inside it.
Winter traction and chain law
CDOT posts traction and chain law signs on mountain corridors, notably I-70 between Floyd Hill and the Eisenhower Tunnel and on Vail and Loveland passes. When the passenger vehicle traction law is in effect, tires must be mud-and-snow rated, or the vehicle must have four-wheel drive or all-wheel drive with adequate tread. When the commercial chain law is in effect, heavy vehicles must install chains or approved alternative traction devices. Chain-up and chain-down areas are signed. Chain law fines are substantial and violators can be required to pay for towing.
Grades, tunnels and mountain hazards
Steep grade signs with percentages, runaway truck ramps built as gravel arrester beds and signed well in advance, and tunnel signs requiring headlights and banning hazardous materials from the Eisenhower Tunnel are common. Watch for ICE ON BRIDGE, blowing snow, high wind, fog and avalanche area signs; an avalanche gate can close a pass with little notice.
Plains weather and wildlife
Eastern Colorado adds dust storm and blowing dust warnings, reduced visibility from ground blizzards, and wildlife crossing signs - deer and elk are most active at dawn and dusk. Open range signs mean livestock may be standing on the roadway.
Worked example
On I-70 westbound you see CHAIN LAW IN EFFECT - TRUCKS ONLY, followed by a chain-up station. The restriction applies to commercial vehicles, not your passenger car, but the traction law still applies to you, and the chain-up area is not a stop for passenger vehicles. Slow down and keep steady momentum on the grade.
Traps
Believing four-wheel drive exempts you from stopping distance - it helps you accelerate, not brake. Treating an avalanche closure as advisory. Missing that a chain law sign may apply only to commercial vehicles. Ignoring ICE ON BRIDGE because the rest of the pavement looks dry.