Wildlife Crossing — Bridges & Culverts

Wildlife Crossing is a structure designed to enable animals to cross a road, railway or other linear infrastructure barrier safely. UK crossings range from large vegetated green bridges spanning motorways down to small mammal pipes and amphibian tunnels installed during scheme construction.

Types of wildlife crossing

Crossing type is selected from species needs, habitat connectivity priorities and scheme constraints:

• Green bridges (ecoducts) — large overbridges 20–80 m wide topped with soil, vegetation and screening. Suit large mammals, deer, badgers; rare in the UK but increasing.
• Fauna culverts and underpasses — dedicated underbridges or oversized culverts with dry passage shelves. Suit medium mammals, otters, badgers.
• Mammal pipes — small culverts 600–1,200 mm dedicated to badgers, otters and other medium mammals. Often retrofitted to existing roads.
• Amphibian and reptile tunnels — 200–400 mm tunnels with directional fencing. Specified where breeding pond connectivity is severed.
• Modified watercourse culverts — natural-bed culverts with mammal ledges that combine drainage with wildlife passage.

Design principles

Effective wildlife crossings share several design principles. The structure must be located where animal movement actually occurs (informed by ecological survey, pre-construction monitoring or known movement corridors). The dimensions must match target species — minimum sizes are set in DMRB LA 109 and CIEEM guidance. Approaches must be funnelled by fencing or planting that guides animals to the structure. Internal conditions — light, noise, microclimate — must be acceptable to the target species.

Monitoring after opening (camera trapping, footprint pads, eDNA) is increasingly required by planning conditions to demonstrate effectiveness.

UK regulatory framework

The DMRB LA 109 (formerly HD 161/03) sets out highway requirements for wildlife mitigation including crossings. The Conservation of Habitats and Species Regulations 2017 and the Wildlife and Countryside Act 1981 drive requirements where protected species are present. CIEEM’s Ecological Mitigation guidance and Natural England standing advice provide design detail.

For badger crossings, Natural England licensing under the Protection of Badgers Act 1992 typically applies. Great crested newt and dormouse crossings are licensed under separate species-specific frameworks.

Related ViaCon solutions

ViaCon supplies corrugated steel culverts ideal for wildlife passage applications — including large pipe-arch and box-section culverts that can accommodate mammal ledges and natural beds. See our bridges and culverts solutions and culverts range. Related glossary entries: culvert pipe, pipe arch and box culvert.

Frequently asked questions about wildlife crossing

{
“@context”: “https://schema.org”,
“@graph”: [
{
“@context”: “https://schema.org”,
“@type”: “BreadcrumbList”,
“itemListElement”: [
{
“@type”: “ListItem”,
“position”: 1,
“name”: “Home”,
“item”: “https://viacon.co.uk/”
},
{
“@type”: “ListItem”,
“position”: 2,
“name”: “Glossary”,
“item”: “https://viacon.co.uk/glossary/”
},
{
“@type”: “ListItem”,
“position”: 3,
“name”: “Wildlife Crossing”,
“item”: “https://viacon.co.uk/glossary/wildlife-crossing/”
}
]
},
{
“@context”: “https://schema.org”,
“@type”: “DefinedTerm”,
“@id”: “https://viacon.co.uk/glossary/wildlife-crossing/#term”,
“name”: “Wildlife Crossing”,
“description”: “A wildlife crossing is a structure designed to enable animals to safely cross a road, railway or other linear infrastructure. UK crossings range from large vegetated green bridges to small mammal pipes and amphibian tunnels, designed per DMRB LA 109 and CIEEM guidance.”,
“inDefinedTermSet”: {
“@type”: “DefinedTermSet”,
“@id”: “https://viacon.co.uk/glossary/#set”,
“name”: “ViaCon UK Glossary”,
“url”: “https://viacon.co.uk/glossary/”
},
“url”: “https://viacon.co.uk/glossary/wildlife-crossing/”
},
{
“@context”: “https://schema.org”,
“@type”: “Article”,
“@id”: “https://viacon.co.uk/glossary/wildlife-crossing/#article”,
“headline”: “Wildlife Crossing”,
“description”: “A wildlife crossing connects habitats across roads and railways. Learn types — green bridges, fauna underpasses, mammal culverts — and DMRB design.”,
“inLanguage”: “en-GB”,
“isPartOf”: {
“@type”: “WebSite”,
“url”: “https://viacon.co.uk/”,
“name”: “ViaCon UK”
},
“about”: {
“@id”: “https://viacon.co.uk/glossary/wildlife-crossing/#term”
},
“author”: {
“@type”: “Organization”,
“name”: “ViaCon UK”,
“url”: “https://viacon.co.uk/”
},
“publisher”: {
“@type”: “Organization”,
“name”: “ViaCon UK”,
“url”: “https://viacon.co.uk/”,
“logo”: {
“@type”: “ImageObject”,
“url”: “https://viacon.co.uk/wp-content/uploads/viacon-logo.png”
}
},
“mainEntityOfPage”: “https://viacon.co.uk/glossary/wildlife-crossing/”
},
{
“@context”: “https://schema.org”,
“@type”: “FAQPage”,
“@id”: “https://viacon.co.uk/glossary/wildlife-crossing/#faq”,
“mainEntity”: [
{
“@type”: “Question”,
“name”: “What is a wildlife crossing?”,
“acceptedAnswer”: {
“@type”: “Answer”,
“text”: “A wildlife crossing is a structure designed to enable animals to cross a road, railway or other linear infrastructure barrier safely. Types include green bridges, fauna underpasses, mammal pipes, amphibian tunnels and modified watercourse culverts. UK design follows DMRB LA 109 and CIEEM guidance, with size and form matched to target species.”
}
},
{
“@type”: “Question”,
“name”: “Do wildlife crossings actually work?”,
“acceptedAnswer”: {
“@type”: “Answer”,
“text”: “Well-designed crossings are highly effective. Long-term monitoring on European motorways and increasingly in the UK shows large mammal collisions can be reduced by 80%+ where green bridges and underpasses are correctly sited and funnelled by fencing. Effectiveness depends critically on siting in actual movement corridors and on guiding animals to the structure.”
}
},
{
“@type”: “Question”,
“name”: “How big should a wildlife crossing be?”,
“acceptedAnswer”: {
“@type”: “Answer”,
“text”: “Size depends on target species. Large mammals (deer, wild boar) need green bridges 40–80 m wide. Medium mammals (badger, otter) accept fauna culverts of 1.2–2 m clearance. Small mammals and amphibians use pipes of 200–600 mm. Minimum sizes for each species group are set in DMRB LA 109 and species-specific Natural England guidance.”
}
},
{
“@type”: “Question”,
“name”: “Are wildlife crossings required by law?”,
“acceptedAnswer”: {
“@type”: “Answer”,
“text”: “Yes, where protected species are affected. The Conservation of Habitats and Species Regulations 2017 and the Wildlife and Countryside Act 1981 require mitigation where roads or rail schemes affect protected species. Natural England issues species-specific licences and conditions. CIEEM guidance and DMRB LA 109 set the technical standards for highway schemes.”
}
}
]
}
]
}