I-70 Winter Traction Law and a 6% Grade
You are westbound on I-70 approaching the Eisenhower Tunnel in February at 6:40 a.m. A variable speed limit sign shows 40 mph. A flashing amber sign reads 'TRACTION LAW IN EFFECT'; a second sign, 'PASSENGER VEHICLE CHAIN LAW,' is dark. Your two-wheel-drive sedan has all-season tires with about 5/32 inch of tread; you carry cable chains in the trunk but have never installed them. The grade ahead is 6% for six miles, and a runaway truck ramp sign is posted. Traffic is moving at 45-50 mph. Your passenger says the flashing sign is only a recommendation and that the tunnel closes anyway. You feel the rear tires slip slightly on packed snow at the tunnel approach. A Colorado State Patrol car is parked near the chain-up area. You are due at a ski area by 8:00 a.m.
1. What does 'TRACTION LAW IN EFFECT' require, and do your tires meet it?
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The Traction Law requires adequate traction for all vehicles, generally tires rated for mud and snow or tires with at least 3/16 inch of tread. Your tires have about 5/32 inch, which is less than 3/16 inch (6/32 inch), so they do not meet the tread standard. The fact that they are all-season tires does not by itself make them compliant if the tread is worn below the threshold. The dark 'PASSENGER VEHICLE CHAIN LAW' sign means that stricter requirement is not the one currently displayed, but the illuminated Traction Law is still regulatory and enforceable. You may not simply proceed because traffic is moving at 45-50 mph; other drivers' behavior is not a legal defense. Your choices are to install the chains you carry, obtain compliant tires or chains, or turn around and wait for conditions to improve.
2. Should you use the runaway truck ramp for the slight tire slip? What is the ramp for?
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No. A runaway truck ramp is for a vehicle that has lost braking ability or control on a steep downgrade, not for minor wheel slip on packed snow. Using it for a traction problem can damage the vehicle, endanger you, and take the ramp out of service for a driver who actually needs it. The slight slip is a warning to reduce speed, increase following distance, use a lower gear, and address the traction-law compliance problem before committing to the grade. The 6% descent for six miles means brakes and traction both matter, but the ramp is not a general emergency pull-off. If you cannot meet the traction requirement, the correct judgment is to stop at the chain-up area, install chains, or turn around, not to aim for the ramp.
3. How should you handle the speed, the grade, and the passenger's advice?
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The 40 mph variable speed limit is a posted limit in the direction of travel, not an advisory suggestion, and traffic moving at 45-50 mph does not raise it. You should slow before the tunnel approach and descend in a lower gear rather than riding the brakes. The State Patrol car near the chain-up area is a reminder that traction and speed requirements are enforced. Your passenger's claim that the sign is only a recommendation and that the tunnel closes anyway is not a reason to proceed illegally. If you install chains, do it in the designated area and keep speed low enough for the chains. If conditions or your equipment do not allow compliance, delaying the ski-area arrival is the safer and legally defensible choice.