Green building is in, and that includes roads and streetscapes.

But unlike building construction, which has the U.S. Building Council’s LEED rating system, the nation’s highway system doesn’t have a green rating system of its own.

Highways, roads, and infrastructure projects are not specifically addressed by LEED standards. They can be designed and built in a sustainable manner, “but there aren’t an equivalent set of standards to LEED,” Nancy Somerville, executive vice president and CEO for the American Society of Landscape Architects (ASLA), tells Better Roads.

LEED, the common term for the Leadership in Energy and Environmental Design Green Building Rating System, was developed by the U.S. Green Building Council in 1998 to provide a set of standards for environmentally sustainable construction.

ASLA has been involved in trying to develop LEED-type standards that would apply to a broad range of design sites, whether it’s a streetscape, a highway corridor — everything from the building on out. In fact, just two months ago, in early November, The Sustainable Sites Initiative — a partnership between ASLA, the Lady Bird Johnson Wildflower Center at The University of Texas at Austin and the United States Botanic Garden — began accepting applications for pilot projects that will test the first national rating system for sustainable landscapes. The application process opened on Nov. 5, 2009, and will close on Feb. 15, 2010, in conjunction with the release of the next report and new rating system, online at www.sustainablesites.org.

Until now, design and construction rating systems included little recognition for benefits of sustainable landscape and site design. Yet landscapes can clean water, reduce pollution and restore habitats, all while providing significant economic benefits to land owners and municipalities.

“Roads are a huge part of our urban fabric…but stormwater runoff from roads is the No. 1 cause of pollution in urban watersheds,” Somerville says. “It’s very significant and hard to deal with because it’s not just like dealing with a factory — a single location. It comes from an entire city.”

That’s why all of the “connective tissue” is key, Somerville points out. Streetscapes can use a system of stormwater planters to manage stormwater runoff. “Roads can be designed so that waste from it is diverted off the road and into the planters,” she says. “By doing that, you’re significantly reducing the amount of stormwater. A lot of this can be done as a retrofit project.”

Without vegetation, a site loses its natural capacity for stormwater management, filtration, and groundwater recharge, according to The Sustainable Sites Initiative (Go to www.sustainablesitesinitiative.org  for more information.) Reduced vegetative cover also affects soil health, because vegetation maintains soil structure, contributes to soil organic matter, and prevents erosion. Through evaporation, transpiration, and the uptake and storage of carbon, trees and other vegetation moderate the climate of the world and provide a breathable atmosphere.

Portland, Ore., is one of a growing number of areas that is retrofitting its streetscapes to be more sustainable. Portland has redesigned its streetscapes with stormwater planters.

Houston also has integrated sustainability and stormwater management into its vegetation and erosion control plans along city highways. “Houston has done a good job of how it has dealing with vegetation along areas of its highways,” Somerville says. The area along highways is usually depressed so it collects water. But in Houston, the area along the highway is designed to collect water runoff.

“This keeps stormwater from rushing into the systems, but being used for the vegetative system,” Somerville points out. “The soil does a significant job in filtering the water.” In fact, she says, “it’s doing a lot to actually clean the water.” Vegetating the areas along the roadways and highways also provides air-cooling benefits.