Apr 12, 2024 - News

I-70's variable speed limits cause confusion for drivers

 A variable speed limit sign on I-70. Photo courtesy of CDOT

A variable speed limit sign on I-70. Photo courtesy of CDOT

If you don't know the speed limit on Interstate 70, you're not alone β€” and it's not your fault.

A 10-mile stretch of the eastbound lanes recently moved to variable speed limits (VSL) between Georgetown and Idaho Springs during extreme weather and times of congestion.

  • One recent day the electronic signs showed 65 mph before falling to 45 mph, then increasing and decreasing by 5 mph repeatedly over miles.

Why it matters: If you can't trust a speed limit sign to remain constant, then what can you trust?

Driving the news: The state transportation department made the shift to variable speed caps to better manage traffic conditions and reduce crashes in the tight stretch where weather, downhill stretches and congestion often cause delays.

  • The I-70 section is the first in the state to use automated software that ties traffic volumes and crash rates, as well as weather, to recommend speed limits.
  • The speed can go as low as 30 mph on the interstate in icy or wet conditions, officials say.

What they're saying: "This helps to prevent crashes and 'stop and go' traffic. VSLs have been shown to improve safety and operations on highways nationwide," Colorado Department of Transportation's Jessica Myklebust said in a statement.

Yes, but: It doesn't necessarily work all the time β€” whether because drivers intentionally ignore the speed limit or continually need to brake and speed up to match the ever-changing signs.

  • The posted speed is enforceable by law enforcement, and it applies to the tolled express lane.

The big picture: Colorado transportation officials are increasingly relying on automated variable limits to control traffic, deploying them already in Glenwood Canyon and soon in other areas, including Wolf Creek Pass.

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