Highways are disastrous for the environment. These wide, dangerous roadways can cut wildlife from the resources they need to thrive, causing them to make the perilous journey from one side to the other. Countless animals have become roadkill as a result, not to mention the many drivers who have perished upon colliding with a deer or some other large animal. From the 1950s onwards, many countries in Europe have dealt with the problem by creating wildlife overpasses—structures that are designed to blend in with nature and that allow the animals to safely cross sides. As National Geographic reports, more and more places around the world have started to create wildlife overpasses over the years to protect their precious animals. There are overpasses used by moose in Canada, bobcats in Montana, and crabs on Christmas Island. With every project, researchers learn more about how animals interact with the passageways. As it turns out, different species prefer different types of crossings. For instance, elk and grizzly bears like big, open structures while cougars, accustomed to forests, prefer more constricted passings with more cover. And it’s not only overpasses that are spreading across the world; underpasses are becoming popular too.  These passageways are usually compact, and so are especially helpful to smaller animals—water voles in London, badgers in British Columbia, pumas in Brazil—but in Kenya larger ones are even being used to assist elephant herds. Us humans have to recognize that our highways are a danger to wildlife. At least with these over-and-underpasses, we have an effective way to reduce the harm.