· the right tree · in the right place ·
· for the right reason ·

Safer, more Permeable Roads

Safer, more Permeable Roads: Learning from the European Approach

Darryl N Jones
Environmental Futures Centre,
Griffith University, Brisbane, Qld, Australia.

Executive Summary

Recognition of the impact of transportation infrastructure on ecosystems and biodiversity is transforming the planning, design and construction of roads throughout the world. Although much of the research and influential reviews associated with the new field of road ecology appear to originate in North America, this perception is partly due to a focus on English language sources. In reality, the development of responses to the impact of roads on natural systems in the European Union has led to a remarkably mature approach across Europe, as evidenced by the high standards or practice and the sheer scale of the measures in place and planned. Given the general lack of readily accessible information on what can be called the European Approach to the ecological impact of roads, and the rapidly growing need for knowledge that may aid the development of the field in Australia, this review aims to address the following questions:

Contemporary European policies and practices have had a long history of development, originating in the environmental positions present in the early European Community. Especially influential have been Directives of the European Commission which oblige European Union Member States to comply and enshrine the policies in national legislation. In particular, the 'Birds' (1979) and 'Habitats' (1992) Directives have been instrumental in ensuring international responses to the protection of sensitive species and sites from the impacts of developments. Critically, the designation of a large number (over 20,000) of sites distributed throughout Europe and known as the Natura 2000 network posed a major challenge to the expansion of transportation infrastructure. The key response to this challenge was via the formation of the Infra Eco Network Europe (IENE), an international group of road planners, researchers, policy developers and NGOs. Using funds from the European Commission, IENE undertook a hugely ambitious cooperative project (COST Action 341: Habitat Fragmentation due to Transportation Infrastructure) involving 16 countries over six years. This project synthesised all existing information and practice, producing a series of products the most significant of which were The European Review (2002) and The European Handbook (2003).

The 'Handbook' has proved to be the single-most important influence on the responses of the diverse range of countries, providing both clearly stated concepts as well as detailed technical details and recommendations which are capable of straight-forward translocation into road design. This has enabled the crucial outcome of the implications and mitigation of impacts to be considered at all stages of project development and implementation. That is, full integration into the road design process.

The efficacy of the European approach can be seen in its practical responses to the three-stage process of minimising impact: first, avoid (sensitive sites or local disturbances); then mitigate (any impacts, usually through the construction of fauna passages); and, as a last resort, compensate (unavoidable impacts by careful off-setting or financial recompense).

Avoidance of sensitive sites can be attempted at both the route alignment phase and at the local scale, the latter involving a range of design options that ensure that impacts on sensitive sites (especially watercourses) are entirely eliminated (such as through broad avoidance bridging). The most effective and impressive of all such structures are undoubtedly the new-generation viaducts. Although the primary driver for the installation of these extremely expensive structures has been the necessity for very flat roads, carefully considered pillar-centric construction techniques have dramatically reduced disturbance to the land below. The extensive use of tunnelling has also had many biodiversity benefits.

The mitigation of impacts has certainly become the most active area of development and innovation, with many engineering solutions being employed with the overall aim of de-fragmentation by enabling the safe movement of animals across roads. Underpasses are now routinely designed to fit specific target species, and are increasingly placed in relatively high densities (every 300m is recommended). Various raised platforms - either included in the design or retro-fitted - are also commonplace now.

The most conspicuous manifestation of the European approach to reducing fragmentation is the many and varied overpass designs now present in hundreds throughout the region. From the earliest structures designed simply to allow deer movements (due to pressures from the still powerful hunting lobbies), overpasses are now broader (50m is the recommended minimum width), often longer (the largest are over 1km in length) and increasingly planted to attract a wider range of species. Barriers to reduce traffic sound and noise are important elements of current underpass design.

The last and least defined measure is that of compensation. Considerable debate continues at what may be regarded as suitable or adequate off-set provisions, although important approaches to this vexed area have been recently developed.

Finally, the issue of monitoring must be regarded as an essential element of the overall approach. Only by intentional and carefully formulated assessments can improvements and adaptations continue to lead to better fulfilment of the aims of the de-fragmentation. In particular, attention must be direct toward evaluation of the effectiveness of mitigation plans at the population level.

In conclusion, Australian agencies and road engineers have much to learn from the processes and practices now well established across Europe. In particular, consideration of measures that aim to ameliorate the impacts associated with roads must start to be included at all phases of the development of a project, and especially at the earliest strategic scoping stages.

Safer, more Permeable Roads: Learning from the European Approach - Full Text (PDF) 2,054KB

Related Australian Research

Jones, D. N. and Bond, A. R. F. (2010), Road barrier effect on small birds removed by vegetated overpass in South East Queensland. Ecological Management & Restoration, 11: 65-67. doi: 10.1111/j.1442-8903.2010.00516.x

Abstract available from: Wiley online library

Jones, D. N., Bakker, M., Bichet, O., Coutts, R. and Wearing, T. (2011), Restoring habitat connectivity over the road: vegetation on a fauna land-bridge in south-east Queensland. Ecological Management & Restoration, 12: 76-79. doi: 10.1111/j.1442-8903.2011.00574.x

Abstract available from: Wiley online library

A cut and cover style overpass

land bridge

↑ Top of Page