System acts as wildlife crossing guard

If this were another road, Colorado transportation officials might fence it off to keep the animals from crossing. But the one-mile portion of U.S. Highway 160 is an important migration route for wildlife.

So the state is trying a different approach: an intrusion detection system that until now has been used to guard military bases and prisons and to protect the homes of the rich.

An approaching animal triggers electromagnetic changes in the ground that are detected by a sensor, which activates a sign warning motorists of the animal's presence.

If the $1-million experiment proves successful, it could provide Colorado with a new method of managing wildlife on roads without cutting off deer and elk from their migratory patterns. For decades, states have used fences to dissuade wild animals from entering roads. Such measures -- as well as underpasses and overpasses -- have proved effective, said Marcel Huijser, research ecologist for the Western Transportation Institute at Montana State University in Bozeman.

Over the last 15 years, some states have experimented with other ways to warn motorists of crossing animals, which can weigh hundreds of pounds and total a car.

Some systems use microwave, infrared or laser-beam technology to detect animals breaking a barrier, which causes the sign to light up with a warning. In Washington, one system detects radio-collared elk in the vicinity.

Such systems are new enough that their effectiveness is not yet known, although some studies indicate they may reduce collisions by as much as 82%, Huijser said.

But they also can be problematic, activating warnings when the systems are tripped by pockets of hot air, traffic, low-flying birds or snow sprayed by plows.

"All of those [systems] work, but they're very high-maintenance," said Michael McVaugh, a traffic and safety engineer for the Colorado Department of Transportation.

For several years, he and other engineers have searched for a solution for U.S. Highway 160, a two-lane road that runs between Durango and the smaller community of Bayfield. The road is notorious even in southwest Colorado, where wild animals are the leading cause of crashes, Transportation Department spokeswoman Nancy Shanks said.