But until now, no single highway plan has pulled all of them together, said Victor M. Mendez, the head of the Federal Highway Administration. “This innovative approach is what we’re looking for in the future,” he said. “It’s an exciting project.”

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Donald E. Hunt, the executive director of the Colorado Department of Transportation, said when the first shovels turned dirt on U.S. 36 that the idea of offering many ways to travel on one road was simple: “More transportation options mean less time sitting in traffic.”

U.S. 36, which opened as a toll road in 1952 at a cost of $6.3 million, was designed with expectations that it would carry 3,000 cars a day by 1980. In fact, nearly 14,000 cars a day were rolling down the highway by 1966, and these days the average is between 80,000 and 124,000. Over time, “transportation investment didn’t keep up with development,” said Audrey DeBarros, the executive director of 36 Commuting Solutions, the 14-year-old organization that pushed for the plan.

By 2005, the highway transportation research group TRIP ranked U.S. 36 as No. 1 among the state’s “heartburn highways,” based on poor maintenance, congestion and accidents.

Fixing this is not easy, and it will take years. Workers are replacing bridges over the highway to accommodate the extra lanes and creating temporary lanes on the shoulders so traffic is not squeezed by the construction and many objectives can be accomplished at once. “There’s no alternate, parallel way to get to Denver,” said John Schwab, the director of the lanes project for the Colorado Department of Transportation. “It’s a very important corridor for all of the residents.”