Roadkill is a serious problem. In the United States, wildlife causes more than one million automobile accidents every year. They cost $8 billion. That includes money spent on medical care and fixing the vehicles. More than a million animals are killed every day by cars. For many species, it is the main cause of death.

Another problem is that major roads separate animal populations. They also destroy their habitats. It becomes hard for animals to find food.

Keeping Animals Safe

Highway crossings for animals are becoming more common. There are different kinds of crossings. It depends on the species that need to cross. It also depends on geography. Bridges, overpasses and tunnels are the most common. They reduce the number of crashes. They also give animals a safe way to cross a road.

Wildlife bridges are usually covered in plants. It makes them look natural. Animals are more likely to use them. Often fences are placed on the side of the road. They direct wildlife toward the crossing.

Wildlife crossings began in France in the 1950s. It took off in the Netherlands. More than 600 crossings have been built there. The Dutch built the world's longest animal crossing. It is more than 0.8 kilometers (0.5 miles) long. In the United States, the idea took longer to catch on. Wildlife crossings began here less than 20 years ago.

A Tunnel for Frogs

In 1995, Davis, California, built a tunnel to let frogs pass under a road. One end was decorated to look like a frog village. It was named Toad Hollow. The frogs never used it.

Banff National Park is in Canada. The crossings there are more successful. Between 1996 and 2016, 42 crossings were built. In that time, 150,000 animals have used them. The number of accidents involving wildlife went down 80 percent.

Bridges for Koalas and Deer

In Queensland, Australia, koalas (Phascolarctos cinereus) have been disappearing. Auto accidents were one of the main causes, the government said. Queensland built about six crossings. The koalas began using the tunnels very quickly.

Western U.S. states are building animal crossings. In 2018, Washington was building bridges across Interstate 90. They will allow animals to pass between the northern and southern Cascade Mountains. Deer already began using one. It wasn't even finished yet.

Wildlife crossings can be expensive to build. They save money in the long run, though.