WASHINGTON  At a picturesque spot in the mountains near the ski resorts of Vail and Breckenridge, Colo., two streams of traffic converge: people driving east and west on Interstate 70, and animals  black bears, cougars, bobcats, elk and deer  headed north and south to feed and mate. When they collide, the animal is almost always killed and the vehicle badly damaged, even if the driver is lucky enough to escape injury.

The obvious solution is a bridge or a tunnel for the animals, but how do you build one they will use?

On Sunday, a nonprofit group announced the winner of a competition to design such a crossing: Michael Van Valkenburgh & Associates, a landscape architecture firm with offices in New York City and Cambridge, Mass. The design team, associated with the national construction firm HNTB, submitted a proposal for a bridge made of lightweight precast concrete panels that are snapped into place and covered with foliage.