A bill that got initial approval in the Colorado legislature Thursday requires passenger vehicles to have tires or chains capable of keeping them moving on Interstate 70 from Morrison to Dotsero from Nov. 1 to May 15 each year.

Under the proposal, noncommercial drivers must respect the chain laws that affect commercial vehicles or face a $100 fine plus a $32 surcharge. The fine jumps to $500 if they block the road.

Heavy costs are dealt to the ski resorts, other businesses and commercial truckers when I-70 shuts down — an estimated $800,000 to $1 million an hour, or about $143 million last year, said Rep. Diane Mitsch Bush, D-Steamboat Springs.

“This bill is not only about safety, but it’s also about reducing some very negative economic consequences,” she said.

Mitsch Bush added, “This updates our chain law to bring (passenger vehicles) into compliance with what’s already required of truckers.”

The bill passed the voice vote with no one raising an objection. The bill could move to the Senate if it passes a second roll-call vote in the House within the next few days.

Mountain travelers would need a tread depth of one-eighth of an inch. Tire experts recommend holding a quarter in the tread, with Washington’s head upside down. If you can see all of his skull, your tread is too worn to safely drive in snow.

The legislation would require the Colorado Department of Transportation to post signs along I-70 — as well as social media and public relations campaigns — that notify travelers of the requirement.

A legislative analysis projects that most people will comply. A law would bring in less than $5,000 a year in fines. In January, I-70 averaged 33,439 vehicles a day at the Eisenhower Tunnel.

Joey Bunch: 303-954-1174, jbunch@denverpost.com or twitter.com/joeybunch