Climatic conditions at timber overpasses for wild animals

Overpasses for wild animals are being made out of timber for the first time in Switzerland. Bern University of Applied Sciences is evaluating the general climate conditions by systematically monitoring the climatic and humidity conditions at the Swiss timber bridges.


  • Lead school(s) School of Architecture, Wood and Civil Engineering
  • Institute Institute for Timber Construction IHB
  • Funding organisation Bundesamt für Umwelt BAFU
    Wald- und Holzforschungsfond WHFF
  • Duration (planned) 01.07.2020 - 30.06.2022
  • Project management Andreas Müller
  • Head of project Marcus Jacob Schiere
  • Project staff Sébastien Bonifacio
  • Partner Timbatec Holzbauingenieure Schweiz
    Häring AG und Roth Burgdorf AG
    terra vermessungen AG
    Lignum Holzwirtschaft Schweiz
    Lignum Compact
  • Keywords Overpasses for wild animals, wooden bridges, wood moisture, monitoring systems, road building


Timber is now also being used in the construction of overpasses for wild animals in Switzerland. The initial positive experiences and findings from four overpasses for wild animals constructed in Germany since 2005 have provided a solid planning framework.

Woods with higher natural durability, such as larch and Douglas fir, were used for these overpasses in Germany. But they are not available regionally in sufficient quantities in Switzerland for structures of this nature and scale. A chemical wood treatment is being used to improve the durability of spruce and fir trees available in Switzerland. However, this raises the issue of whether the use of chemicals is really necessary.


The project aims to record and scientifically evaluate the general climate conditions by systematically monitoring the climatic and humidity conditions at the structure. Special emphasis is placed on the impact of traffic. The timber construction is exposed to large volumes of water from spray clouds. On the other hand, the traffic has a positive impact on air change (flow) in the structure and on its drying capacity.

The impact of the cross-sectional shape and design of the tunnel-like bridge structure on the moisture levels and drying speed of the wood will also be analysed.


The outstanding issues will be resolved as part of a comprehensive analysis of climatic conditions at overpasses for wild animals through long-term monitoring, laboratory testing and simulations. The results will be presented in an application-oriented research report with observations on the design of timber overpasses for wild animals.