Underpasses built along the Delhi–Dehradun Expressway are being widely used by wild animals as intended, according to a study commissioned by National Highway Authority of India (NHAI).
The study, conducted by the Dehradun-based Wildlife Institute of India, is based on field monitoring conducted between May 16 and June 24, 2025, along the Ganeshpur–Dehradun stretch.
The findings, released by NHAI on Friday, come ahead of the inauguration of the Delhi–Dehradun Expressway by Prime Minister Narendra Modi on April 14.
The 210-km access-controlled corridor, expected to cut travel time between Delhi and Dehradun from over six hours to about 2.5 hours, features India’s longest wildlife corridor and dedicated wildlife crossings along forest stretches.
The stretch falls within the Shivalik elephant corridor and along the edge of Rajaji Tiger Reserve, part of the Terai Arc Landscape, a key biodiversity region. As part of the project, a network of underpasses and elevated sections along the alignment, including an 11-km-long stretch, was designed to allow animals to move beneath the road.
A total of 40,444 wildlife detections from over 111,000 images captured using 150 camera traps over the 40-day period.
Nilgai, elephants, jackals, hare, sambar and spotted deer were among the early users, while species such as leopards and rusty-spotted cats appeared later in the sampling period, suggesting variation in behavioural adaptation.
The study used a Relative Abundance Index (RAI), calculated as the number of independent captures per camera-trap day to estimate how frequently species used the crossings. Ungulates and mid-sized mammals dominated the usage. Nilgai (RAI 16.76), sambar (15.07) and spotted deer (7.72) were among the most frequent users, along with golden jackals (21.05), which recorded the highest relative abundance among wild species. Elephants were also detected, though at lower frequencies (RAI 1.04), indicating use of the structures by large mammals as well.
Human presence remained significant across the underpasses, said the report with people, livestock and vehicles, often exceeding wildlife detections.
Spatial patterns were uneven. Heat map analysis showed that certain sections, particularly towards Ganeshpur recorded higher activity for species such as leopards and Indian hare, while other stretches saw lower usage. For elephants, crossings were clustered at specific points, indicating preferred routes rather than uniform movement across the alignment, the study said.
However, temporal analysis showed that many species adjusted activity patterns to avoid disturbance. Leopards and several ungulates were largely nocturnal, while human and vehicular movement peaked during daytime.
The study also incorporated acoustic monitoring using AudioMoth devices to assess the effect of traffic noise. It noted that vehicular noise can influence animal behaviour and habitat use, sometimes creating a “phantom road” effect even beyond the physical highway.
