"Deer and motor vehicles do not share the nation's highways gracefully or safely," the study noted. "Deer inhabit all of the United States, including Hawaii, where they have escaped from captivity." Furthermore, deer-related crashes are on the rise, as both deer populations and vehicular travel continue to increase.

Deer population is difficult to estimate, but some estimates put the total U.S. deer population at more than 25-to-30 million, the researchers said.

But among the numerous attempts made in the past to reduce deer crashes, only one method has proven to be consistently effective. The study said that fences--combined with underpasses and overpasses--are the "only broadly accepted method that is theoretically sound and proven to be effective." But it is still not a perfect solution--fences are expensive to construct and maintain, and even the best fencing will not prevent all deer from entering a roadway.

The study found there are some promising new approaches that could lower deer-related crashes in the future. One is herd reduction, which, as part of an overall wildlife management program, can be effective if the deer population in a specific area is reduced substantially.

Roadside clearing--along with better roadway design and maintenance as well as warning signs--can also be effective, the report said.

Another strategy is to equip cars with infrared technology that can detect deer and other heat-emitting objects on the road. These devices have recently been added to high-end personal automobiles, including Cadillacs by General Motors, the study said.