In the U. S. state of Washington, a road called Interstate(州际公路；州际的)90 cuts through a wild mountainous area to reach the city of Seattle. For the area's many kinds of animals, busy high- way greatly limits their movements. Animals need to move to find food, to find mates, to find new places to live as their populations expand or just when conditions change, like a fire breaks out. Crossing I-90 – as the road is called – is a risky but sometimes necessary act. But soon, animals will have a safer choice. They will be able to go above it.
To help the animals, the state is finishing work on its largest - ever wildlife bridge. The 11-meter-tall, 20 - meter - wide bridge begins in the forest. It forms two arches above the highway, one for each direction of traffic. Workers are adding fencing anti plants to help guide the animals across the bridge, Two-meter-thick walls will help block noise from vehicles below. Scientists chose the area because it is within a natural migration(迁徙)path for some animals.
The I -90 bridge is part of a growing number of wildlife crossings across the United States. Some are fences, some are overland bridges，and some are underpasses. They all aim to keep drivers and animals away from each other.
A U. S. Transportation Department study found crashes between animals and humans rose year by year. The accidents made up about 5 percent of all crashes nationally, and cost the economy (经济)about ＄8 billion. Such costs come from car repaid, emergency room visits and removal of the dead animals on roads. Collisions between animals and drivers are rarely deadly to people. But they are often deadly to wildlife. The study also found that 21 endangered or threatened species in the U.S. are affected by vehicle hits. Bridges, underpasses and fencing reduce I he area's animal - driver collisions by 80 percent.
Most of the wildlife bridges are in western states. Many other areas also need such paths. But finding money for more crossings is "the- number - one problem". Patty Garvey — Darda of the U. S. Forest Service has worked on the I - 90 crossing from the start of the project. She says the $ 6 - million bridge will one day pay for itself because the highway will not have to be fully or partly closed each time a large animal is struck. "If you shut clown Interstate 90, you shut down interstate trade." she adds.
