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When transit riders take their first rides on TriMet’s new Orange Line, they’ll probably 鈥渙oh鈥� at the public art along the 7.3-mile route. They’ll likely 鈥渁hh鈥� as they glide past the Tilikum Crossing, Bridge of the People. But there’s a good chance the slickest 鈥� and greenest 鈥� feature of the new light-rail extension that runs from Portland to Milwaukie will go largely unnoticed.

Among the sustainable features TriMet added to the Portland-to-Milwaukie light-rail line is a vegetated trackway featuring a stretch of brightly-colored sedums 鈥� hardy, low-maintenance vegetation commonly used on eco-roofs.

Though the 鈥渆co-track鈥� extends only a few hundred feet, TriMet was proud enough to use an image of it on the cover of its sustainability report, 鈥淢aking the Orange Line Green.鈥� TriMet spokeswoman Mary Fetsch said it was an appropriate image to reflect what she called the agency’s most sustainable light-rail project to date.

鈥淲e always look to pilot new technologies and sustainable practices and as the eco-track is the first vegetated trackway in the U.S., it seemed a natural fit to be the cover photo of our sustainable report,鈥� Fetsch said.

With a price tag of $1.5 billion, the Orange Line is the sixth major construction project on the MAX light-rail system, and the most expensive. The line runs between Portland State University and North Clackamas County and expands TriMet’s total light-rail service to 60 miles and 97 stations.

For the eco-track, TriMet went with Ramos Construction to install soil, irrigation and 4,000 square feet of sedum mat at the Southwest Lincoln Street station. Ramos went with Washington-based Etera, a manufacturer of vegetated roofing tiles.

Vegetated roofs, also known as green roofs or eco-roofs, are a sustainability measure intended to reduce conventional tar- or rubber-based roofing materials. They’re said to beautify as well as reduce heating and HVAC use, and aid in stormwater management.

The Orange Line eco-track was selected to provide similar stormwater control benefits.

Etera’s sedum mats are innovative in several ways, according to company spokeswoman Darcy Drysdale. All tiles feature a coconut fiber base to aid plants in rooting. The mats achieve 鈥�100 percent鈥� plant coverage, so it’s difficult for weeds to move in 鈥� a common issue with green roofs. And the standard square size of the tiles allows for easy packing and quick installation.

One worker can put down 1,800 square feet per hour, Drysdale said.

鈥淚t just lays down super-flat,鈥� she said. 鈥淵ou get the roof you want the day you install it.鈥�

Etera’s tiles begin life in the company greenhouse in Mt. Vernon, Washington. After seven to ten days inside, they’re transferred to nearby fields to harden off. After four weeks, they’re stacked on pallets, shrink-wrapped with breathable netting, and shipped.

Because Etera ships throughout the U.S., it’s developed blends that thrive in the nation’s distinct geographies. The 鈥淭uff Stuff鈥� mix 鈥� made of hardier varieties 鈥� does better in drier climates.

Though it had never made an eco-track before, only a few minor tweaks were needed to meet TriMet’s needs, said Drysdale.鈥淭he standard tiles fit their plans really well,鈥� said Drysdale.

Etera has bred several of its own colors, several of which can be seen in Portland. For the eco-track’s colors, TriMet selected one variety of sedum spurium, — 鈥淩ed Carpet鈥� 鈥� and five varieties of sedum album 鈥� 鈥淐oral Carpet,鈥� 鈥淢urale,鈥� 鈥淕reen Ice,鈥� 鈥淥range Ice鈥� and 鈥淐hloroticum.鈥�