As Ty Barger lurched up the side of Yankee Boy Basin, the Jeep Gladiator’s engine whined. He advanced slowly, occasionally peeking his head out the window to check how much room he had between his tire and the edge.

Until recently, the roads leading to the Mt. Sneffels Trailhead had been treacherous for most vehicles. He took no chances with that in mind.

“There are a lot of spots where you don’t have a lot of room,” said Barger, Ouray County’s road and bridge superintendent.

For the past...