UK's Biggest Green Bridge Built Over A3 for £3.7M
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- Cockrow Bridge cost £3.7m — about 1% of the £317m M25 improvement scheme — and was built by excavating and transplanting lowland heath from either side of the A3 onto the structure, with heather, sand piles for sand lizards, and cooling logs already in place.
- National Highways built the crossing to reconnect Wisley and Ockham commons, which the A3 had split for decades; despite not yet officially opening, foxes, roe deer, and adders have already been recorded using it.
- James Herd, Surrey Wildlife Trust's director of reserves management, said the A3 had caused 'genetic isolation' on the commons and warned that dedicating 1-3% of every road scheme to a greening element would be 'the shrewdest investment you could make'.
- The UK lags far behind on wildlife crossings: the US has more than 1,000 animal crossings, and the Netherlands has built about 80 green bridges since 1988, including the 800-metre Natuurbrug Zanderij Crailoo — the world's longest.
- Dr Silviu Petrovan of Cambridge University's zoology department said Britain is 'one of the most fragmented countries in the world' due to the density of its road network, and that green bridges increase habitat resilience by allowing populations to recover through recolonisation.
- The UK's State of Nature report found average abundance of 753 terrestrial and freshwater species has fallen about 19% since 1970, with 16.1% of more than 10,000 assessed species threatened with extinction — context Herd cited when warning the country is heading toward 'ecosystem collapse' if it does not act swiftly.
Why it matters: Herd's 1% proposal reframes a £3.7m bridge as a template: if applied across the UK's road network, even a sliver of future scheme budgets could begin repairing the habitat fragmentation that National Highways' own adviser calls a major driver of nature loss. The international comparison — 1,000+ crossings in the US, 80 in the Netherlands, and only 'a few' in the UK — shows the gap is policy, not biology.
