Roads of the future: Roads hold America together, but at a cost. Now, thinkers are starting to imagine—and engineer—a better way

boston.com:

SINCE OUR NATION’S earliest days, America has been fixated on our roads, be they yellow brick, high or low, or the one less traveled. The United States has 4 million miles of roads, covering a surface area equivalent to that of South Carolina. They represent freedom, possibility, connection, and even escape. They are the circulation system of our culture and economy, shaping where we live and work, how we transfer goods, how we access services.

But roads have another side as well: a harmful one. Roads are the site of 30,000 deaths every year, but even beyond the obvious dangers, the network has its own, unintended effects on the country. Roads erode soils, trap heat, and disrupt wildlife habitat; they are expensive to create and even more so to maintain.

We’ve long fantasized that ultimately we’d see roads disappear completely, as Doc Brown suggests at the end of the classic 1985 movie “Back to the Future”: “Where we’re going, we don’t need roads.” He’s talking about 2015, a time when, as we see in the sequel, people are flying in hovercraft. But as 2015 approaches, we still rely on roads as the backbone of our transportation networks, towns, and cities. As engineers, city planners, and “road ecologists” are realizing, we do need roads. We just need better ones.

A road may seem so basic as to be unchangeable — a strip of asphalt or concrete laid across the ground. But in recent years, researchers have started to ask imaginative questions about how roads work and don’t work — not just in their immediate impacts, but in the way they affect animals, water, energy use, and quality of life for people. They have begun to propose creative, even radical solutions to the problems that roads can cause, using everything from better highway design to smarter asphalt to reduce roads’ harmful effects. And though it’s still in early stages, some of this work goes even farther, plotting a future in which roads are not just a necessary evil, but can bring unexpected benefits to the land around them.

WHEN YOU’RE DRIVING on a highway through a vast desert or forest, it can seem as if the road is an insignificant part of the landscape. But that’s an illusion. Though roads are conduits for one kind of movement, they’re barriers as well: they block ancient patterns of animal migration and cause countless wildlife deaths every year. They help spread invasive plant species by dispersing seeds and allowing them to gain a foothold along the roadside corridor, while fragmenting and isolating native populations. That isolation can disrupt usual breeding patterns, making populations less genetically diverse and more vulnerable to being wiped out by catastrophic events.

The ecological effects of roads extend beyond the road surface; Richard Forman, an ecologist at Harvard, estimates that one-fifth of the nation’s land is directly affected by roads. Noise from heavily trafficked roads can inhibit bird densities and breeding for several hundred yards on either side. The construction, use, and maintenance of roads causes erosion and spreads pollutants into surrounding air, soil, and water. Roads and related structures like culverts also disrupt water flows and wetlands, which can have far-reaching impacts on humans and other species. In fact, while roads may seem like an innocuous and narrow disruption, they actually amount to a re-engineering of habitat on a vast scale.

Forman is one of the founders of road ecology, the study of roads’ effects on ecosystems. The discipline was founded in the 1990s, and research from the field is finally beginning to yield practical innovations in road design. Joseph Burns, who works in transportation ecology and species protection for the National Forest Service, says that a paradigm shift is taking place in the way highways are constructed. “Instead of breaking up systems — whether human communities or natural processes — now they’re more permeable.” To take one example, traffic collisions had been one of the top killers of Florida’s panthers, one of the most endangered animals in the country. When a series of highway underpasses was built along I-75 in the 1990s, the panthers began using them for safe passage across, lowering collisions on the highway.

Wildlife overpasses and underpasses now straddle highways and roads throughout the country, particularly in the Rockies and in Florida, where large animals are frequently hit by cars. Bill Ruediger, a wildlife consultant in Montana who has been involved in over 100 wildlife crossing projects over the past decade or so, says that animals readily learn to use these structures. Although the will to build crossings is highest where collisions with large animals cause injuries and cost money for travelers, conservation activists and biologists are also looking for solutions for small animals like salamanders and frogs, whose survival depends on the connection of far-flung populations.

The flow of wildlife is not the only thing historically disrupted by roads: there’s also the flow of water. Burns says that engineers are now taking waterways into account in considering how to plan and rebuild roads. Where highways once barreled through floodplains, they are now built to bridge them, which preserves water stores and habitat while also protecting roads from costly washouts. Roads that work with water systems, he says, “are adaptable and more cost effective.” He adds that if designed correctly, such roads can even provide a service, withstanding the peak flows while helping to hold water in dry times…

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