The Robert LB Tobin land bridge in San Antonio, Texas, spans a six-lane highway and provides a safe crossing for wildlife including deer, coyotes, and bobcats, as well as pedestrians. Located within Phil Hardberger Park, a 311-acre public space, the bridge is part of a larger effort to restore native Texas prairie—one of the most endangered ecosystems in North America, with only 1% remaining.
Park Origins and Vision
The park is named after Phil Hardberger, mayor of San Antonio from 2005 to 2009, who campaigned on improving public parks despite advisers warning that such focus was “soft stuff” that would not win votes. Hardberger believed the city should prioritize quality of life over mere growth. The park was built on a former dairy farm and features mature oak trees, including a 400-year-old specimen.
Design and Ecological Balance
Landscape architecture firms Stimson Studio and Rialto Studio preserved or restored 75% of the park’s area to prairie land, with the remaining 25% designated for picnic areas, an urban ecology center, and parking. “The balance is in favor of wildlife and nature,” said Lauren Stimson, a principal at Stimson Studio. Eight miles of trails wind through native grasses, shrubs, and wildflowers such as magenta Texas thistle and yellow creeping oxeye.
Addressing the Highway Barrier
A freeway built in the 2000s cut through the open space, threatening biodiversity by fragmenting the ecosystem. Inspired by European wildlife crossings, Stimson Studio designed a land bridge accessible to both people and animals that reads as a natural extension of the park. The bridge is 150 feet wide at its midsection. To minimize disturbance to wildlife, pedestrian areas are pushed to one side, with a steep berm and plantings buffering the two groups.
Eight-foot-tall steel walls block views of the highway and shield animals from headlights and noise. The bridge is a few degrees warmer than the rest of the park due to heat-retaining materials like stone and metals, and because young plants produce less evapotranspiration than the adjacent established oak savanna. Circular cutouts provide airflow.
Wildlife Use and Monitoring
The land bridge opened in 2020. Within six months, wildlife biologists observed coyotes, deer, bobcats, and small mammals crossing it. Migratory birds also pass through; conservationists have counted more than 180 species, including the Nashville warbler. “Connectivity is an extremely important part of ecology,” said Gregory Tuzzolo, an associate principal at Stimson Studio. “You can make a conservation area over here and a park over there, but if wildlife can’t pass from one area to another, we still have a degraded landscape.”
The park also features viewing sheds adorned by local artists, a native plant wildscape demonstration garden, and ADA-compliant winding elevated walkways with a 5% grade.
