Once the tracking data pinpointed areas with high crossing rates that weren't close to any underpasses, the biologists added motion sensors linked to warning lights to cover those stretches. Measures of traffic speed demonstrated that stationary wildlife warning signs had virtually no impact on drivers. 

The crossings have proven so successful that Arizona now plans to install a similar network along Interstate 17 near Flagstaff. In addition, the state is working on crossings to protect a herd of bighorn sheep near Hoover Dam that frequently crosses Highway 92. 

The combination of new research, worrisome lawsuits and pressure from conservation groups has dramatically increased interest in wildlife crossings among traffic engineers. It's one of the rare environmental gains in recent years. 

"I've been working on this issue for seven years, and on every other issue conservationists have been getting hammered. But on this issue, there's actually been some progress," says Tricia White, director of the Habitat and Highways campaign for Defenders of Wildlife and author of Getting Up To Speed, an activist's guide to the topic. 

Specifically, conservationists won a provision in the 2005 highway bill that requires transportation planners to consult with environmental groups, land-use and wildlife agencies early in the planning process. Previously, pork-barrel politics forced dramatic changes in the original plans and engineers rarely even considered things like wildlife until well after budgets and alignments had already been set, says White. 

Cramer cites a list of projects that prove that careful, early planning not only saves lives; it can avert enough crashes to recover the cost of a project in 10 to 15 years. Although major wildlife crossings can cost millions to retrofit or design, those costs amount to small change on a multibillion-dollar highway, notes Cramer. 

She cites other model projects, including a network of 80 crossings in Florida to protect the endangered Florida panther and Florida black bear, a network of 52 wildlife crossings on Highway 93 in Montana, the Tijeras Canyon project in New Mexico outside of Albuquer-que, 17 crossings on Highway 90 in Washington state, the study of crossings as part of the Southern Rockies Ecosystem Project in Colorado, and landscaped overpasses in Banff National Park in Canada that allow notoriously road-shy grizzly bears to cross a major highway safely. 

Many of those projects have studied Arizona's careful redesign of Highway 260, in part because years of data from the radio-collared elk have provided remarkable insight into the reaction of animals to a busy highway. That underscored the complexity of animal behavior and the need to build that knowledge into the design of freeways, rather than relying on expensive stopgap measures once a highway has fragmented habitats, experienced accidents, and garnered a political constituency. 

The plight of the Florida panther provides one obvious example, notes Cramer. The population of panthers had declined to less than 100 in the 1980s, with rampant development restricting their habitat. After cars killed 16 panthers in a single year, the state built a network of 24 underpasses, dramatically reducing the roadway deaths and helping the nearly extinguished population begin to expand. Florida kept pace with additional underpasses, for both the panthers and for the endangered Florida black bear. The state now boasts 80 specially designed underpasses, making it the number-one state for wildlife crossings. However, continued development and new roads have so fragmented the habitat of the wide-ranging bears and panthers that they're now routinely killing one another in a grim struggle for territory, says Cramer. 

"The number-one solution is to consider wildlife early," says Cramer. "But sometimes that's going to mean maybe you don't build that road." 

Advocates note that careful planning for wildlife makes both environmental and economic sense. For instance, Vermont recently decided to stop putting bridge pilings in the middle of streams. When combined with a design that leaves a shoreline on each side of the stream to allow the passage of animals that don't like to swim, such a redesigned bridge provides a crossing point for a wide array of species. Moreover, Vermont soon discovered that a redesign intended to help fish and animals also saved money, by reducing the maintenance cost associated with the stream-scoured pillars planted in the water. 

Ultimately, planners must sometimes consider whether another highway is even needed, says White, no matter how politically appealing the pork-barrel payoff. 

"A lot of people see roads as inevitable, a necessary evil," says White. But the full impacts of major roads have become increasingly clear, right down to the documented effects on the soil far beyond the edge of the road itself. "So how many more roads are we going to build? The learning curve is very steep at this point; we're just starting to understand the impacts. So let's put the brakes on." 


A Phoenix based-freelance writer and former editor of Arizona Highways magazine, the author has covered environmental issues in the West for 20 years and written 12 books.