A highway kills animals. That much is obvious, and it is the lesser of the two harms it does.
The greater harm has no corpse. A road divides a population that could once breed across a whole landscape into sub-populations on either side of a surface many species will not cross. Ecologists call it the barrier effect, and it raises extinction risk through the loss of genetic exchange even if not one animal is ever struck. Mitigation structures exist for that problem at least as much as for the first — they are about connectivity, not only safety.
Which is why the most informative line in NHAI's document of 8 October 2026 is not the number of structures. It is the money.
What was released
The National Highways Authority of India released a document titled 'Wildlife Mitigation Measures & Structures', marking National Wildlife Week, 2–8 October 2026. It had been released by Shri Nitin Gadkari, Minister for Road Transport and Highways, at a Chintan Shivir held at Ekta Nagar, Gujarat.
The headline figures:
- Around ₹19,700 crore invested over the last five years in wildlife mitigation infrastructure and related environmental protection measures
- More than 2,150 wildlife mitigation structures constructed and/or proposed along National Highways
- Guide fencing and noise barriers provided along over 300 km of National Highway alignments
The document is framed around three named problems — habitat fragmentation, barrier effects and wildlife–vehicle collisions — with planning guided by the ecological sensitivity of corridors, wildlife movement patterns and technical feasibility.
Read the spending, not the count
| Structure | Investment |
|---|---|
| Viaducts | ₹8,300 crore |
| Animal underpasses | ₹4,600 crore |
| Tunnels | ₹2,800 crore |
| Major bridges | ₹2,500 crore |
| Animal overpasses | ₹650 crore |
| Minor bridges | ₹500 crore |
Two things jump out.
First, viaducts are the largest line — bigger than underpasses and overpasses together. A viaduct is an elevated road. Instead of building an embankment and then perforating it with a crossing, you lift the entire carriageway onto piers and leave the ground continuous underneath. That is the strongest mitigation available, because it removes the barrier rather than putting holes in it: an animal does not have to find a designated crossing, because the whole stretch is a crossing. It is also the most expensive thing on the list per kilometre.
Add tunnels at ₹2,800 crore, which achieve the same result in the opposite direction, and ₹11,100 crore of the ₹19,700 crore — more than half — has gone on removing the road from the animal's path altogether rather than on managing the conflict. That is a better record than a count of 2,150 structures conveys, and it is the point the document does not make for itself.
Second, the underpass-to-overpass ratio is about seven to one — ₹4,600 crore against ₹650 crore. That ratio reflects engineering convenience rather than animal preference.
Published monitoring consistently finds that hoofed animals prefer overpasses, or wide and open underpasses, and that sightlines matter to them: a deer or a gaur is reluctant to enter a structure from which it cannot see the far side. Several carnivores, by contrast, use enclosed tunnels readily — long-running monitoring in Banff has documented exactly these species-specific preferences. So the right mix of structures depends on which species use a given corridor.
An underpass is cheap, because an embankment is being built anyway and a box culvert can be sized up. An overpass requires a structure carrying soil and vegetation over live traffic. The 7:1 spend therefore tells you what is easy to build, not what is best to build — which makes the document's claim of ecological-sensitivity-led planning the thing to hold NHAI to, corridor by corridor.
The commitment that makes this auditable
Most road mitigation in the world is built and never evaluated, so nobody knows whether it works. A structure is only mitigation if animals actually use it.
NHAI's document records camera trapping to assess wildlife movement patterns and support periodic evaluation of mitigation measures, alongside identification of wildlife–vehicle collision hotspots with speed-regulation boards and signage. That is the single most important commitment in the document, because it converts a capital asset into a testable claim.
And Indian evidence already shows the method works. On the NH-44 stretch through the Pench landscape, Wildlife Institute of India camera traps recorded 18 species using the crossing structures between March and December 2019. The most frequent users were not the charismatic animals such projects are usually justified by, but small mammals — Indian hares and jungle cats — with tigers, leopards, gaur and sloth bears also recorded, mostly at night.
That finding is worth keeping. A crossing built for tigers turns out to be used overwhelmingly by hares, and that is a success rather than a disappointment: the barrier effect operates on every species, and the small ones have the least capacity to disperse around an obstacle.
Why noise barriers sit beside fencing
The non-structural measures look like afterthoughts and are not. The document lists signage, fencing and speed regulation, plus noise barriers, reptile crossings and rainwater harvesting.
Guide fencing and noise barriers are listed together over 300 km for a reason. Fencing does one job: it stops animals entering the carriageway at random and funnels them towards a designated crossing. Quiet does the other: monitoring on Indian corridors has found that elephants, sambar and spotted deer favour the quieter parts of crossing structures, while golden jackals and wild boar are more tolerant of noise. Fencing gets an animal to the entrance; silence persuades it to go through.
It is also worth noting that the two can conflict. At least one study of railway crossings found that while fencing successfully funnelled most species towards structures, it reduced elephant passage — a reminder that a measure beneficial on average can harm a particular species, and that monitoring is the only way to find out.
Canopy crossings and reptile crossings are the details that signal a serious document. A canopy crossing is a rope or pole bridge above the carriageway for arboreal animals — primates, squirrels, civets — which will not descend to ground level to cross a road at all. A reptile crossing addresses animals that cannot negotiate a kerb. Both are cheap, highly species-specific, and almost always omitted.
Where this sits legally
None of this is voluntary. Linear infrastructure passing through a protected area or an eco-sensitive zone requires clearance involving the National Board for Wildlife and its Standing Committee, and mitigation conditions are imposed at that stage. The structures are, to a substantial extent, the price of clearance — which is why a document cataloguing them is also a compliance record. The institutional machinery is the same as that described in our explainer on the National Board for Wildlife.
The wider conflict is now a standing category of Indian litigation. Transmission lines against the Great Indian Bustard in the Thar, highways against tiger corridors in central India, canals and railways elsewhere — in each case a linear structure crosses a habitat, and in each case the question is whether it can be elevated, buried, or routed around.
That question has a cost, and the honest version of the trade-off is this. Access-controlled highway design, which is where India's high-speed highway programme is heading, makes roads far safer for people by fencing them and removing at-grade crossings. It also makes them more absolute barriers for wildlife, because the fencing that keeps pedestrians off keeps everything else off too. The ₹8,300 crore of viaducts is, in effect, what it costs to have both — and that number is the real measure of how seriously the trade-off is being taken.
🔑 Revision block
- Release, 8 October 2026: NHAI published 'Wildlife Mitigation Measures & Structures', marking National Wildlife Week, 2–8 October. Released by Shri Nitin Gadkari at a Chintan Shivir at Ekta Nagar, Gujarat.
- Headline figures: about ₹19,700 crore over five years; more than 2,150 mitigation structures built and/or proposed; guide fencing and noise barriers over 300 km of alignments.
- Three named problems: habitat fragmentation, barrier effects, wildlife–vehicle collisions.
- The barrier effect: a road divides a population into sub-populations, raising extinction risk through loss of genetic exchange even with zero collisions. Mitigation is therefore about connectivity, not just safety.
- Investment breakdown: viaducts ₹8,300 cr · animal underpasses ₹4,600 cr · tunnels ₹2,800 cr · major bridges ₹2,500 cr · animal overpasses ₹650 cr · minor bridges ₹500 cr.
- Why viaducts are the strongest measure: an elevated road removes the barrier rather than perforating it — the whole stretch becomes crossable. With tunnels, ₹11,100 crore of ₹19,700 crore went on removing the road from the animal's path.
- The 7:1 underpass-to-overpass ratio reflects engineering convenience, not animal preference. Hoofed species prefer overpasses or wide, open underpasses, and sightlines matter to them; several carnivores use enclosed tunnels readily. Banff monitoring documents these species-specific preferences.
- Structure types: Animal Under Passes (AUPs), major and minor bridge-cum-AUPs, culverts adapted for faunal movement, canopy crossings (rope or pole bridges for arboreal species), reptile crossings.
- Monitoring — the key commitment: camera trapping to assess movement and periodically evaluate structures, plus identification of collision hotspots with speed-regulation boards and signage. Most mitigation worldwide is built and never evaluated.
- Indian evidence: on NH-44 through the Pench landscape, Wildlife Institute of India camera traps recorded 18 species using the structures between March and December 2019 — most frequently Indian hares and jungle cats, with tigers, leopards, gaur and sloth bears also recorded, largely at night.
- Noise matters as much as geometry: elephants, sambar and spotted deer favour quieter sections; golden jackals and wild boar tolerate noise. Fencing funnels animals to crossings; quiet persuades them to use one. One railway study found fencing reduced elephant passage even while funnelling other species.
- Statutory frame: linear infrastructure through a protected area or eco-sensitive zone needs clearance involving the National Board for Wildlife and its Standing Committee, where mitigation conditions are imposed.
- The trade-off to state: access-controlled highway design makes roads safer for people by fencing them, and thereby makes them more absolute barriers for wildlife. Viaducts are what it costs to have both.
🎯 Practice MCQs
Q1. The "barrier effect" of a highway refers to: (a) Noise that drives animals away from the surrounding habitat (b) The visual obstruction created by roadside plantation (c) The division of a population into sub-populations, reducing genetic exchange (d) The accumulation of pollutants along the carriageway
→ (c) It raises extinction risk independently of any animal being struck, which is why mitigation is framed around connectivity rather than only road safety.
Q2. The largest single component of NHAI's wildlife mitigation spending over the last five years was: (a) Viaducts, at about ₹8,300 crore (b) Animal underpasses, at about ₹4,600 crore (c) Tunnels, at about ₹2,800 crore (d) Animal overpasses, at about ₹650 crore
→ (a) More than underpasses and overpasses combined — and with tunnels, over half the ₹19,700 crore went on elevating or burying the road.
Q3. A viaduct is a more effective mitigation measure than an underpass principally because it: (a) Is cheaper to construct per kilometre (b) Removes the barrier rather than perforating it, so the whole stretch is crossable (c) Can be built without wildlife clearance (d) Eliminates the need for fencing
→ (b) An animal does not have to locate a designated crossing. It is also the most expensive option per kilometre, which is why the spend figure is significant.
Q4. The roughly seven-to-one ratio of spending on underpasses versus overpasses is best explained by: (a) A finding that most Indian species prefer enclosed structures (b) A requirement in the Wild Life (Protection) Act (c) The absence of suitable sites for overpasses (d) The relative ease and cost of building a crossing into an embankment that is being constructed anyway
→ (d) An overpass must carry soil and vegetation over live traffic. The ratio reflects buildability, not what the animals would choose.
Q5. Published monitoring suggests that hoofed animals generally prefer: (a) Overpasses, or wide and open underpasses where they can see the far side (b) Narrow enclosed tunnels (c) Culverts carrying flowing water (d) Canopy crossings
→ (a) Sightlines are the governing factor for ungulates, whereas several carnivores use enclosed tunnels readily.
Q6. On the NH-44 stretch through the Pench landscape, Wildlife Institute of India camera traps recorded: (a) Only tigers and leopards using the structures (b) No wildlife use over the monitoring period (c) 18 species, with Indian hares and jungle cats the most frequent users (d) Use restricted to the monsoon months
→ (c) The heaviest users were small mammals rather than the charismatic species such projects are justified by — which is a success, since the barrier effect operates on every species.
Q7. Noise barriers are relevant to wildlife mitigation because monitoring indicates that: (a) Noise has no measurable effect on crossing use (b) Elephants and deer favour quieter sections of crossing structures (c) Noise barriers double as guide fencing (d) Noise attracts predators to crossing points
→ (b) While golden jackals and wild boar are more tolerant of noise. Fencing gets an animal to the entrance; quiet persuades it to pass through.
Q8. A canopy crossing is intended for: (a) Reptiles unable to negotiate a kerb (b) Large herbivores requiring open sightlines (c) Amphibians moving to breeding ponds (d) Arboreal species that will not descend to ground level to cross
→ (d) A rope or pole bridge above the carriageway for primates, squirrels and civets — cheap, species-specific and usually omitted.
Q9. Clearance for a National Highway passing through a protected area involves: (a) The National Board for Wildlife and its Standing Committee (b) The Central Pollution Control Board alone (c) The National Green Tribunal in the first instance (d) The Forest Survey of India
→ (a) Mitigation conditions are imposed at the clearance stage, which is why the structures are substantially the price of permission rather than a voluntary measure.
Q10. The tension between access-controlled highway design and wildlife conservation arises because access control: (a) Requires wider rights of way than conventional highways (b) Fences the carriageway, which keeps wildlife off as effectively as pedestrians (c) Mandates higher design speeds inside protected areas (d) Prohibits the construction of underpasses
→ (b) Access control makes a road much safer for people and a more absolute barrier for animals — which is precisely what viaducts and tunnels are bought to offset.
📋 How this gets asked (PYQ pattern)
Infrastructure and wildlife is examined in four recognisable ways, and the first is a concept rather than a fact.
The first is the barrier effect versus direct mortality. Any question asking why crossing structures are built has two possible answers, and the stronger one is habitat connectivity and genetic exchange, not collision avoidance. Candidates who give only the second answer get half the mark.
The second is structure vocabulary. Underpass, overpass (or eco-duct), viaduct, culvert, canopy crossing, reptile crossing. Six terms, each matched to a species group and a cost. A question describing a structure and asking which species it serves is standard.
The third is the clearance chain. The National Board for Wildlife and its Standing Committee for protected areas and eco-sensitive zones; the Forest (Conservation) framework for forest land; the Wild Life (Protection) Act, 1972 for schedules and protected-area categories. Linear projects sit at the intersection of all three.
The fourth, worth most in a written answer, is the trade-off. Being able to state that access-controlled design improves human safety while worsening habitat fragmentation — and that viaducts and tunnels are the expensive way to buy both — shows you can hold two objectives at once, which is what the analytical questions reward.
Preparing for CDS/OTA? When a ministry publishes spending figures by category, divide and compare before you memorise. The ratio between two line items usually reveals the real priority far better than the headline total does. Build the base with our CDS/OTA study material, follow the daily CDS current affairs, and prepare with our faculty in the upcoming Cavalier courses in Delhi.
✍️ Written by The Cavalier — Faculty desk at The Cavalier. Reviewed by the Cavalier Faculty Desk.