Wildlife overpasses are the reverse of most conventional bridges in terms of structural engineering, and this has implications for how they are designed and the materials from which they can be made.
Conventional vehicular bridges are typically longer in span than width; that is, they are narrow enough to accommodate maybe two to four lanes of traffic but may have a long span to cross a river, a highway or a harbour. Wildlife bridges are typically shorter in span but much wider. They also necessarily include a thick layer of soil and vegetation—a landscaped surface—that must emulate local habitats.
This means that crossing structures could be designed differently from conventional bridge structures. They might include lighter, flexible and adaptive materials or a system of construction that is modular or even dynamic.
These innovations can result in more sustainable and affordable construction. An adaptable, modular structure can also expand, contract or be moved to respond to changing habitats and uncertain climate conditions that are difficult to predict.
As a new category of infrastructure, wildlife crossings are an opportunity to explore new materials, features and approaches to building and construction. This exploration is important, given the diversity of habitats and wildlife species that must be accommodated affordably and safely.
The five finalist teams in the ARC International Design Competition did just that kind of exploring. Their creative, collaborative and interdisciplinary design processes resulted in an innovative range of ideas:
The only way to solve the problem of vehicle-wildlife collisions for good is to have a system of crossing structures—overpasses and underpasses, bridges and tunnels. No single structure alone will solve more than a localized problem. ARC’s goal is to make wildlife crossings a ubiquitous part of the North American roadscape. To do this, an adaptable, flexible and modular design is needed—one that can be readily modified to different contexts and circumstances.
One of the simplest and most elegant ways to begin this infrastructural transformation is to use everyday materials that are readily available, but to use these materials in an uncommon and modular way. This is precisely what the winning team proposed.