SEQUIM, Wash. – When elk amble across Highway 101 here on the Olympic Peninsula of western Washington, radio collars around their necks set off flashing lights up and down the busy road.

A continent away, when moose wander across Route 4 in the mountains of western Maine, their hulking bodies break an infrared beam that triggers flashing lights on moose warning signs.

On re-engineered highways between the wireless elk and the beam-breaking moose, there are underpasses for tortoises in California, vibration-detectors for deer in Wyoming, and a 52-foot-wide overpass for deer, foxes, coyotes and opossums on Interstate 75 in Florida.

At an accelerating pace, federal and state highways across much of the United States are being tricked out with critter-crossing technology, high and low. It is an attempt to halt a rising tide of roadkill – the grisly result of more cars, more sprawl and a continentwide resurgence of large hoofed animals, including deer, elk and, deadliest of all, moose.

The scale of America’s roadkill and highway ecology problem is attracting high-level attention after decades of being ignored by highway engineers and regional planning agencies, said Richard Forman, a professor of ecology at Harvard.

“We have come a long way since the mid-1990s, when there was a pitiful amount of information,” he said. “Thinking about road ecology is now permeating state departments of transportation in a very positive way.”

That thinking has also percolated up to Congress. For the first time, the Senate version of a pending transportation bill would require all state transportation departments to consult with fish and game agencies from the beginning of planning for roads built with federal money. Also, for the first time, the Senate bill considers wildlife crossings to be a major safety issue and would allocate federal money for fences, overpasses and other ways of reducing roadkill.

Moose collisions have become so common in Maine that the state Department of Transportation is warning that if the beast is unavoidable, drivers should aim for its tail. That reduces the chance of a 1,500-pound antlered ungulate crashing through the windshield and landing in a driver’s lap.

People are killed or seriously injured in one out of four of the 700 or so moose-vehicle collisions that have occurred in Maine every year for the past decade. Moose (and to a somewhat lesser extent, elk) are potentially lethal because they are tall, with most of their body mass located above the hood of a car. In a collision, a car’s bumper takes out the animal’s legs, while its head and body hurtle toward the windshield. Late spring is high season for these crashes, and Maine had its first fatality of the year last weekend, when a motorcyclist died after hitting a moose.

In the past two decades, moose trouble has spread across much of New England. The number of moose killed by cars in Vermont, for example, jumped from two in 1982 to 164 in 2002, according to the Vermont Department of Fish and Wildlife.

“We have had an explosion of moose in the past decade,” said Eugene Dumont, a wildlife biologist for the state of Maine. “Our habitat is conducive to moose, with less farming and more forest. We have more moose per square mile than anywhere else in North America. Combine that with more traffic and you get more accidents.”

Although moose and elk are the deadliest (to human beings) of animals commonly hit on U.S. highways, the country’s primary roadkill problem is deer.

Like moose and elk, deer numbers have exploded because of less farming and more habitat, including succulent suburban lawns and shrubs. But unlike moose or elk, which are proliferating mostly in New England and the Rocky Mountain West, deer are multiplying everywhere.

More than 90 percent of animal-vehicle collisions in the United States involve deer, researchers have found. In 1995, the annual number of these collisions was estimated at more than 1 million, causing 211 human fatalities, 29,000 injuries and more than $1 billion in property damage.

“All these numbers are now far, far higher than they were in the 1990s,” said Bill Reudiger, ecology program leader for highways at the U.S. Forest Service. He said that the collection of data on roadkill is neither uniform nor reliable, but that “everything suggests this is a bigger problem than most people realize.”

It is a twofold problem. First and most obviously, there is what writer John McPhee has described as the “D.O.R.” phenomenon – creatures dead on the road after high-speed collisions with vehicles. Second, highways carve up ecosystems, isolating animals and fish in ever-smaller, walled-off grids that can push some species toward extinction.

Deer, elk and moose do not seem to mind, but highways are believed to be factors in declines of bears, lynx, wolves and, in perhaps the best-documented case, the Florida panther.

Research has found that flashing animal-warning signs can raise driver awareness, while cutting reaction time in half, said Marcel Huijser, a research ecologist at Montana State University’s Western Transportation Institute.

“The signs can reduce reaction time from 1.5 seconds to .7 seconds,” he said. “If you are traveling at 55 miles an hour, this means you could potentially reduce your stopping distance by 68 feet.”

In Switzerland, where similar warning systems have been in place for 11 years, the number of car collisions with deer and wild boar has been cut by 80 percent, Huijser said.