BOULDER CITY, Nev. (AP) — Four underpasses were built to protect wildlife from traffic and traffic from wildlife on a new stretch of Interstate 11 near Boulder City.

Wildlife officials in Nevada and Arizona plan to use tracking collars and remote cameras to determine whether animals are actually using the several million dollars' worth of wildlife crossings built as part of the first addition to the nation's interstate highway system since 1992, the Las Vegas Review-Journal reported .

The underpasses were inspired by three overpasses just up the highway in Arizona that effectively eliminated collisions between cars and desert bighorn sheep on U.S. Highway 93.

About a dozen bighorns a year were being hit on the highway before the improvements were made, Arizona Game and Fish Department biologist Jeff Gagnon said. That number dropped to five the first year after the wildlife crossings went in, he said.

The bridges were built at a cost of $4.8 million and opened in 2011, after extensive study and consultation with Arizona wildlife experts.

"We haven't had a single accident since 2014," Gagnon said.

When transportation engineers began work on the new stretch of I-11 around Boulder City, Gagnon and company were asked to help consult on the design alongside the Nevada Department of Wildlife.

The collaboration began in 2014, when wildlife experts from the two states teamed up to catch and collar 25 bighorn sheep in the mountains now split by the interstate. The GPS data transmitted by the collars was used to track the movement of the animals before and during highway construction.

Once the batteries ran out on those collars, another 25 sheep were fitted with transmitters last year, allowing the monitoring to continue beyond the highway's official opening on Aug. 9.

The new 15-mile (24-kilometer) stretch of I-11 includes one overpass and four underpasses for wildlife, said Tony Illia, spokesman for the Nevada Department of Transportation.

Gagnon said he expects the I-11 wildlife crossings to see use by a whole range of animals, not just sheep. His department has seen evidence of coyotes, foxes, desert tortoises and even mule deer using the wildlife bridges and tunnels on U.S. 93, he said.

But there's one key difference between two road projects: While U.S. 93 has been around for decades, I-11 presents a barrier that didn't exist before, so biologists can only guess at how wildlife will react.

All of the wildlife underpasses on the project were designed to be as open as possible because bighorns "like to cross over things" not under them, said Brad Hardenbrook, Nevada Department of Wildlife's supervisory habitat biologist for Southern Nevada.

'We'll see just what kind of response the sheep will give us as time goes on," Hardenbrook said.

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Information from: Las Vegas Review-Journal, http://www.lvrj.com