Few of us think twice about driving on roads. Yet the very presence of roads and the act of driving on them can impact the ecological infrastructure that supports an animal's daily life. What chance does a turtle have of successfully laying its eggs when it needs to traverse a busy highway? Is it realistic to expect small mammals to breed when an interstate thoroughfare subdivides their population? These are the sorts of challenges faced by small, often slow-moving, animals, challenges that road engineers and ecologists are trying to address.

For countless small species, vehicles...