Dedin Green Bridge — Wildlife Overpass Monitoring on the Zagreb–Rijeka Highway (Croatia)

When Croatia built its Zagreb–Rijeka highway (A6) through the core forest habitat of Gorski Kotar, engineers included a single purpose-built 100 m-wide green bridge at Dedin alongside 43 viaducts and tunnels, aiming to keep the region's brown bears, wolves and Eurasian lynx connected across the barrier.
Infrared-sensor monitoring at the Dedin bridge logged 12,519 animal crossings over 793 active monitoring days – an average of 15.8 crossings per day – with ungulates (roe deer, red deer, wild boar) accounting for 83.2% of movements and large carnivores 14.6% (Kusak et al., European Journal of Wildlife Research, 2009).
A separate three-year study (2009–2011) at four other A6 green bridges – Ivačeno brdo, Medina gora, Varošina and Osmakovac – compared track-pads, camera traps and infrared detectors as monitoring methods, recording bear, wolf, deer, wild boar, fox, badger, marten and hare use, and finding infrared detectors registered far more raw events than cameras before filtering for false triggers (Gužvica et al., PLOS ONE, 2014).
Radio-tracking of collared carnivores found bears, wolves and lynx strongly preferred large tunnels and viaducts over small underpasses, a design lesson now used to size future crossings; the Dedin bridge's usage matched its available share of the landscape, indicating the purpose-built structure performed acceptably but was not markedly preferred over the highway's other large structures.

Read the full analysis: https://www.wolf.org/wp-content/uploads/2007/10/Kusak-et-al.-2009-The-permeability-of-highway-in-Gorski-kotar-Croatia-for-large-mammals.pdf