|A bat bridge on the A590 in Cumbria|
Bats tend to follow linear features in the landscape when foraging at night, at least in part because they provide protection from predators. Bats tend to avoid flying over open spaces. Hedgerows, edges of woods, and so on, form commuting routes between roosting and feeding sites for bats. When these are damaged or destroyed, for instance by road building, bats either lose feeding locations or have to cross the open space. Usually they do this by flying low: effective against their age-old predators, but not much help when confronted by a car.