Moving people safely across the region on new and improved multimodal roadways and expanded transit systems is a primary goal of the Regional Transportation Authority plan.
In addition, the voter-approved plan funds projects for wildlife to safely move through natural habitat that intersects with regional transportation corridors.
“When the (RTA) road plan was passed in 2006, it was the first plan adopted by voters in this country that included an amount specifically for wildlife linkages infrastructure,” Carolyn Campbell, board member with the Coalition for Sonoran Desert Protection, said at a recent Pima Association of Governments’ Environmental Planning Advisory Committee.
Campbell also was a long-serving member of the RTA Citizens’ Advisory Committee, which was responsible for helping develop the first RTA regional transportation plan approved by Pima County voters in 2006, and she was involved in the most recent plan development efforts associated with RTA Next.
Since 2006, the RTA plan has funded approximately 40 wildlife crossing structures, including bridges and culverts, throughout Pima County to improve wildlife safety linkages. The most notable of these is the wildlife bridge that spans Oracle Road, also known as State Highway 77, in the northern section of Oro Valley.
This structure, completed in 2016, was built in coordination with the Arizona Department of Transportation (ADOT) while the agency worked on improvements to the highway. As part of this same project, the RTA provided funding to construct a large arch culvert beneath the roadway. Several miles of fencing was later installed along the roadway corridor to direct wildlife to the crossing structures.
“It was the RTA plan element with the most flexibility,” said Ellis. “It allowed us to invest in the necessary research, infrastructure improvements and retrofit opportunities.”
The inclusion of wildlife linkage structures in the RTA plan was informed by previous research by ADOT and the Arizona Game and Fish Department on ways to protect wildlife through preserving habitat connectivity. The wildlife bridge on Oracle Road, for instance, preserves the connection between the Santa Catalina Mountains and Catalina State Park and the Tortolita Mountains. Its location was selected based on additional studies of wildlife movements, including roadkill analysis to identify areas of frequent animal and vehicle conflict.
In the years since passage of the plan, the science of locating new structures evolved and improved through the work of the RTA Wildlife Linkages Working Group and ongoing monitoring at the locations where structures have been built.
Ellis said the knowledge collected has helped transportation and wildlife officials understand the different behaviors of desert dwelling animals, as opposed to mountain and forest fauna, and develop linkages effectively.
“This has given us the ability to determine what is the smartest thing for us to do and identify best opportunities to do it,” Ellis said.
The approach has worked and can be measured by the effectiveness of the wildlife crossing structures that have been built in the region.
Game and Fish Department data from nearly eight years of monitoring at wildlife crossings showed the RTA-funded structures on Oracle Road have received heavy use. This included nearly 10,000 mule deer, 2,900 javelina, 1,165 coyote, and 148 bobcat crossings at the Oracle Road overpass.
The underpass on Oracle Road, too, has been heavily used by animal species, including one documented mountain lion. Monitoring found 36 distinct native vertebrate species using the crossing structures.
The RTA project on Tangerine Road – La Cañada to Interstate 10 – included five wildlife crossing underpasses. These structures are drainage facilities that were upsized plus incorporated additional features that were more wildlife friendly, so they could serve as effective wildlife crossing structures. Monitoring at these structures, which were constructed in 2018, also showed frequent use by a variety of native species. From 2018 to 2024, more than 30,000 animal crossings were documented at these structures.
Campbell, who was an early proponent for inclusion of the wildlife linkage element in the RTA plan, said the successes of the environmental element have been gratifying, noting the need to overcome skepticism when the plan was proposed.
“The public sentiment shifted,” she said.
Additional RTA-funded wildlife linkage projects include the La Cholla corridor project, Tangerine Road to Magee Road, which has four wildlife underpass structures upgraded from drainage facilities. In addition, improved crossing structures were installed on Highway 86 in the Tohono O’odham Nation.
Wildlife linkage features have been included on RTA-funded projects on Twin Peaks Road, Camino de Mañana, Ina Road and Sahuarita Road. In addition to helping land-based animals, RTA bridge projects have included bat boxes, which are structures installed on the underside of bridges to provide roosting habitat for native and migratory bat species.
Learn more about the voter-approved RTA plan here.