Should mitigation structures replace avoiding protected areas when aligning highways? Critically analyse.

NHAI's October 2026 document reports about ₹19,700 crore spent on wildlife mitigation over five years. It counts more than 2,150 structures, built and/or proposed [1]. Mitigation reduces harm but does not remove it. Structures should therefore add to avoidance of protected areas, not replace it.

Arguments for relying on mitigation structures

• Animals use them: the NHAI–WII study "Landscapes Reconnected" recorded 18 wild species and 60 elephant crossings through underpasses on the Delhi–Dehradun corridor [2].
• Some roads cannot be moved: NH 715 already runs past Kaziranga. Animals cross it to escape monsoon floods, so moving the road is not realistic [3].
• Design standards exist: NTCA–WII guidance (underpass height ≥ width) [4] and NBWL prescriptions [5] set clear technical rules.

Arguments against replacing avoidance

• Harm remains: traffic noise shrinks habitat. At Kaziranga, hog deer avoided noisy roadside strips even where no animals were hit. This is the barrier effect [3].
• Built for big animals: of 1,176 roadkills on NH 715 in 2019, reptiles were about half and large mammals only 3.48% [3]. NHAI still classes reptile crossings as "non-structural" [1].
• Money spent, not animals saved: only about ₹5,250 crore goes to animal-only crossings. Viaducts and tunnels are often needed for the terrain anyway. "Built and/or proposed" mixes finished work with plans, and there is no national before-and-after roadkill data [1].
• Too few deaths recorded: carcasses of large mammals disappeared within 12 hours [3]. A 40-day camera study may miss the monsoon peak in deaths [2][3].
• Moral hazard: the promise of crossings can make routes through tiger reserves look acceptable. That turns the precautionary principle upside down.

Way forward

• Apply the mitigation hierarchy (avoid → minimise → mitigate) in EIA and NBWL clearances [5].
• Run year-long before-and-after roadkill surveys across all animal groups [3].
• Treat small-animal passages as engineered structures with their own budget. Use seasonal speed limits on flood-escape stretches. Report completed structures separately from proposed ones.

Mitigation structures are essential for fixing existing roads, but they should not justify new roads through protected areas. Following the avoid-first sequence fits Articles 48A and 51A(g) and SDG 15. It lets highway connectivity and ecological integrity move forward together.