Improving road permeability for wildlife faces challenges with population growth. Egnatia motorway in Greece is an example, where part of its network exhibited a quick species´ post-construction recovery. The increasing number of animal-vehicle collisions necessitated urgent installation of a reinforced fauna fence, and tailored mitigation measures to improve permeability of existing crossing structures. During the LIFE SAFE-CROSSING project (LIFE17NAT/IT/464, 2018-2023) interventions were implemented in 55 underpasses. Specific criteria were used to select the location and type of improvements. To evaluate the effectiveness of interventions, an innovative, end-to-end wildlife monitoring solution was developed, which not only monitors the use of underpasses by wildlife, but also assesses automatically the photos/videos collected from solar-panel/battery powered cellular/4G cameras and provides meaningful results (species categorization, statistics, alerting). Conclusions can be summarized as follows:
1. Technical works and removal of debris in modified culverts with a small Openness Index significantly increased motorway permeability for Brown bears.
2. Special defragmentation interventions (like stairs and ramps) on technically fragmented structures have been proved very effective, as they have started to be used by wildlife, especially by the Brown bear.
3. As expected, ungulates respond negatively to underpasses with a small Openness Index, with the Roe deer being the most sensitive species recorded. Hence, Roe deer can be used as an indicator species to evaluate road permeability for the whole spectrum of species in the area.
4. Further monitoring efforts and adaptive management/maintenance are necessary to safeguard road permeability and maintain landscape connectivity for wildlife.

Wildlife crossing structures are commonly installed on roads and railways globally to improve ecological connectivity and fauna movement. While many studies demonstrate use by a wide range of species, very few have evaluated effectiveness. We conducted an extensive literature review and synthesis to address the question: What is the evidence that wildlife crossing structures mitigate the barrier effect of roads on wildlife movement? Specifically, we investigated whether wildlife crossing structures prevented an expected decline in cross-road movement, restored movement to pre-construction conditions, or improved movement relative to taking no action.
We found and analysed 313 studies with 799 datasets and found only 14% of studies evaluated whether wildlife crossing structures resulted in a change in animal movement across roads. We identified critical problems in existing studies, especially the lack of benchmarks (e.g., pre-road, pre-mitigation or control data) and the use of biased comparisons. Wildlife crossing structures allowed cross-road movement in 98% of datasets and improved movement in ~60%. In contrast, the decline of wildlife movement was prevented in fewer than 40% of datasets. For most structure types and species groups there was insufficient evidence to draw generalisable conclusions.
The evidence indicates that wildlife crossing structures can mitigate the barrier effect of roads on wildlife movement, but in many cases have been poorly evaluated. To improve confidence in determining the effectiveness of mitigation at restoring movement, we recommend a thorough evaluation that includes benchmark comparisons, particularly for measures and species that lack sufficient evidence (e.g. invertebrates, amphibians, reptiles, birds, and overpasses).

Collisions between wildlife and vehicles or roadkill remain a persistent issue. This poses a significant threat to the safety of both wildlife and drivers. The lack of systematically managed roadkill records poses challenges for nationwide research and comprehensive assessment in South Korea. Since 2018, the Ministry of Environment (MOE), Ministry of Land, Infrastructure and Transport (MOLIT), and National Institute of Ecology (NIE) in South Korea have been implementing roadkill investigations and management. The areas selected for roadkill mitigation measures were determined through hotspot analysis based on nationwide roadkill data collected using the Korean Roadkill Observation System (KROS), an integrated online platform. In this study, the top 50 roadkill hotspots were selected, and appropriate mitigation measures, including wildlife fences, warning signs, and speed enforcement cameras, were implemented. A total of 190.6 km of wildlife fences, 75 warning signs, and 27 speed enforcement cameras were installed. The results of these implementations revealed an average reduction in roadkill incidents of 80.2%. Subsequently, we compared and analyzed roadkill incidents before and after these mitigation measures were implemented. The comparative analysis based on hotspot grades showed that areas with lower grades had relatively lower reductions in roadkill incidents. Moreover, the study showed that the presence of multiple mitigation measures in a single area did not significantly differ from the effects of a single mitigation measure. This research will contribute to an enhanced understanding of roadkill mitigation measures and aid in preventing wildlife accidents on the road.

Effective measures to mitigate the negative impacts of transport infrastructure are critical to the successful conservation of species threatened by habitat fragmentation. This is particularly important in the human-dominated landscape of Central Europe where isolated populations of large carnivores have been recovering in recent decades. In this study, we used GPS telemetry to assess how the Czech landscape, heavily fragmented by various types of transport infrastructure, affects the dispersal of grey wolf, Eurasian lynx and brown bear. We analysed the movement patterns of 7 lynx, 18 wolves and one bear collared between 2017 and 2024 and compared them with connectivity models, wildlife corridors and the distribution of green bridges. We also focused on frequently crossed road sections within home ranges of collared individuals as well as critical road sections where vehicle collisions with large carnivores have been reported. We discuss the differences in habitat and traffic intensity around critical road sections and make recommendations for future mitigation measures.

In order to recognize how underpasses can contribute to the avoidance or reduction of barrier effects on small animal populations and the ecosystems they shape, the use of differently (size, habitat elements, entrance area) designed structures by different species groups was surveyed.
The indicators were ground beetles, grasshoppers, butterflies, dragonflies, reptiles, mice and shrews. In the case of amphibians, it was wrongly assumed that sufficient information exists, even for longer tunnels. The passages effectiveness was measured by comparing activity in the centres with that in the entrance and surrounding areas (pitfall and camera traps, transect counts, observation of flight behavior, mark-recapture).
Overall, underpasses could significantly reduce the barrier effect of transport infrastructure, but most are dysfunctional due to insufficient width or height, unfavourably designed access areas and poor maintenance. It is crucial for small animals that the access areas have a high habitat suitability for the species concerned and there is great potential for enhancement here, which can be utilised cost-effectively. The requirements for the necessary dimensions of underpasses are high for numerous species and species groups and have so far been underestimated. With an openness index (OI=b*h/l) of < 3 and only a moderate density of individuals in the access area, there is no functionality for many species in need of protection. In order to avoid excessive fragmentation, the widening of tunnels (the necessary OI increases with the length of the passage!) and in many cases (wide or bundled transport infrastructure) the installation of complementary overpasses must be considered.

The upgrade to a 2x2 lane configuration on the A79 (France, Allier) initiated a comprehensive environmental operation program with a strong focus on biodiversity. This includes extensive ecological connectivity structures, stream restorations, and ecological engineering in mitigation areas. This operation program was coupled with a demanding monitoring program assessing the effects of the implemented measures on biodiversity. One year after the implementation, the monitoring highlighted the success of these measures across various faunal groups, including several conservation-sensitive species (bats, European brook lamprey, European wildcart, European pond turtle). This project illustrates the biodiversity restoration potential of linear infrastructure, particularly in the context of upgrading work.

We explored the effectiveness of seven existing road underpass-crossing-structures along the TRAC N4 highway, Gauteng Province, South Africa, for wildlife crossings, with a special focus on vertebrates. The underpasses comprised of; three circular, two rectangular, and one box culverts as well as one large bridge. These were monitored continuously using mounted camera traps from April 2023 until April 2024. Two cameras were deployed in each of the underpass crossings to capture vertebrate animals that enter and exit the structure at both ends, with the larger bridge being monitored by four camera traps. The preliminary camera trap results showed increasing animal activity and use of the monitored underpasses, with twelve different mammalian, three reptilian and six aves species recorded using them for crossing beneath the highway. Although the majority of the animals travelled through the entire length of the crossing structure (complete crossing) animal use of the underpass structures for crossing was greatly influenced by the characteristics of the crossing structures (size, shape, and adjacent roadside habitat type). Underpass crossings with a waterbody underneath were less preferred by terrestrial animals, only Cape clawless otter, Water mongoose and several water birds used them for crossing. This shows that gathering baseline data on wildlife roadkill, animal movement, and behaviour patterns across roadways could help improve planning for ecological connectivity. We recommend that exploring wildlife use of crossing-structures should consider monitoring existing road-crossing structures (culverts, bridges, and tunnels) as this provides a less costly method of restoring landscape connectivity in road fragmented ecosystems.