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Over- and underpasses for reindeer



The Swedish Transport Administration will be required to build over- and underpasses for reindeer on many major roads and railways within the reindeer husbandry area. The passages shall contribute to reducing reindeer roadkill, as well as securing the reindeer’s needs for free movements.

The situation for reindeer (and moose) in the north is special, due to the seasonal migrations and the fact that the animals need to be able to leave certain areas completely during parts of the year. The reindeer’s natural migrations are a prerequisite for the traditional reindeer husbandry; this applies to both the droving of herds and the animals´ free roaming. This means that the requirements for the functionality of fauna passages must be formulated differently and probably set higher than in south Sweden. Accordingly, design requirements and efficiency criteria for fauna passages as well as ambition goals expressed in current guidelines may need to be regionally adapted.

This adaptation requires basic knowledge of the design of fauna bridges for effectiveness for reindeer and reindeer husbandry. Already today, many bridges of different sizes and designs are used by reindeer, to a greater or lesser extent, regardless of whether they are constructed for reindeer use or not. Some bridge design factors are strongly cost-driving, such as size, soil and local topography. Knowledge of how well the various bridges work for reindeer is necessary in order to be able to build cost-effective passages in the future, i.e. passages that meet the requirements without being unnecessarily costly.

Reindeer approaching an underpass. Photo: TRIEKOL


This project studies the reindeer’s use of a number of existing bridges in Norrbotten; same bridges that are also studies within TRIEKOL subproject 3 on over/underpasses for wildlife. The studies are carried out in dialogue with the Sami villages concerned. Data collection takes place mainly through camera surveillance, and primarily includes free ranging animals. The data collection took place during the years 2018-2021.

The project also includes developing and proposing methods and criteria for efficiency assessment of bridges for reindeer and reindeer husbandry. The methods can for example consist of calculating the number of animals or groups of animals using the bridges per unit of time, number of individuals of different animal sex or age class, records of marked or known individuals, studies of vigilance behaviors or speed of movement. Examples of efficiency criteria may be that a certain proportion of the reindeer concerned must be able to pass, that the bridge allows all animals classes to pass, or that the animals must pass without showing disturbed behavior.


The project will show how efficient existing bridges are for reindeer, both those constructed for reindeer and others, and point out how bridges could be adapted to increase their efficiency.

The project provides a basis for calculating the cost-effectiveness of different bridge types and bridge sizes. The results thus provide a basis for efficient design of future bridges for reindeer, and can possibly be used to point out optimal design for some standard types of reindeer bridges.

Contact for the subproject

J-O Helldin

Forskare, SLU Centrum för biologisk mångfald

+46 (0) 706-07 53 22