A crossing guard for deer and elk

On a quiet sage- and pine-dotted stretch of highway in southwest Colorado, deer and elk wander into the paths of oncoming cars so often that they account for 70% of the crashes that occur there.

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. Sensors detect approaching animals and activate a sign warning motorists.

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 for southwest Colorado, where wild animals are the leading cause of crashes, Transportation Department spokeswoman Nancy Shanks said. The stretch is especially dangerous during the spring and fall when animals are moving to the high or low country.

Local concern took on urgency last year when a Colorado State Patrol trooper trying to avoid a herd of deer died in a motorcycle crash.

“It brought home the fact this can happen,” said Dave Wegner, a Durango scientist who heads a La Plata County advisory board on living with wildlife. “This gave us a push to do something.”

For wildlife advocates like Wegner and state officials, fencing off the road wasn’t an option.

“If I put a barrier on the road, the herd counts would decline. They wouldn’t get to a lower range,” McVaugh said.

Then officials learned of a new security system and decided to try to adapt it for their own purposes.

A cable -- buried a foot deep and 30 feet from either side of the road -- detects changes in the Earth’s electromagnetic field caused by the presence of large animals. Creatures smaller than 100 pounds won’t trigger it, McVaugh said.

The information is sent to a sensor module, which activates electronic signs warning motorists.

In a three-year experiment, the state will study whether motorists change their driving habits -- such as slowing down -- in response to the flashing signs.

Officials have installed seven speed detectors to measure drivers’ speeds before and after they see the signs.

“Changing human behavior is not easy, but they’re much more predictable” than animals, McVaugh said.

If officials deem the system a success, they may deploy it elsewhere in the state.

However, detection systems are expensive to buy and maintain. Systems such as the one on U.S. Highway 160 cost between $800,000 and $1 million per mile and are projected to last about 10 years. Fencing the same length of road costs $70,000 and lasts longer.

If officials ultimately do choose a detection system, McVaugh said, they’ll use it in combination with fencing -- installing it at cutouts where animals are permitted to cross the road.

“It is not a silver bullet or should be used everywhere because of the expense,” Wegner said. “But in specific locations, I think it has a lot of potential.”

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deedee.correll@latimes.com