Wildlife & Traffic

A European Handbook for Identifying Conflicts and Designing Solutions

7 Fauna Passages and other Technical Solutions
Original version (2003) - New version will be available by the beginning of 2022 -
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7.5 Reducing the barrier effect and mortality: other measures

7.5.1 Adapting road width and reducing traffic intensity

The barrier effect of roads for small animals is partly an effect of the width of the tarmacked surface. The number of vehicles and their speed, however, also affect the number of animals killed. Different types of measures can be beneficial for wildlife:

Reducing the width of the infrastructure

  • Agricultural and forestry roads which are not tarmacked are more easily crossed by small animals, e.g. invertebrates.
  • On agricultural roads an alternative to a fully tarmacked road is the provision of two concrete tractor-strips. The area between the strips is kept vegetated, thus providing cover for invertebrates

Reducing the amount of traffic

  • Temporary closure of roads is a suitable measure in cases where animals only cross a road during a limited period. It is recommended, for example, to protect amphibians on their migration to spawning grounds (closure during humid nights in spring) or to allow wild reindeer to move to their wintering grounds undisturbed (closure of a road during critical periods in winter).
  • Any other common measure to reduce the amount of traffic (one-way streets, restricted access, etc.) can also be used as a measure to reduce collisions with wildlife.

Reducing the speed of the vehicles

  • Reducing the width of the road can reduce the speed of the vehicles and thus reduce the risk of collisions with mammals. This measure is suitable for rural roads with relatively light traffic.
  • Temporarily or permanently lowered speed limits at high-risk spots can contribute to reducing the risk of collisions with mammals.
  • Where collisions happen mainly during the night, speed limits at night might be sufficient.
  • Speed ramps are recommended on roads with light traffic.
Figure 7.97 - Traffic calming measures reduce the barrier effect and the number of collisions. A: original situation. B: reducing the speed limit. C: reducing speed and traffic capacity by narrowing the road. D: dead-end: reducing traffic by stopping transit traffic. E: reducing speed by speed ramps. F: replacing road with two concrete strips still allows agricultural traffic and reduces the barrier for invertebrates.

7.5.2 Decommissioning of infrastructure

The decommissioning of roads or railway lines should be considered in particular where new infrastructure is constructed. If stretches of old infrastructure are completely removed and the ground returned to nature, this may be considered as a compensation measure for the additional habitat fragmentation created by the new infrastructure. However, in most cases, an old infrastructure will not be completely removed but will for example be used as a footpath or cycleway. Thus it may contribute to reduced habitat fragmentation at a small scale.

Decommissioning of infrastructure should be part of the general planning procedure (see Chapter 5).