Level crossings and wildlife warning systems


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New measures are needed to prevent both wildlife-vehicle collisions and barrier effects. At-grade fauna passages (in Swedish VGU terminology: “faunapassage i plan”) may provide a cost-efficient alternative to under- and overpasses, even if only for larger species and under certain conditions.

The idea of at-grade fauna passages is to direct the movement of animals  across the road to a certain location, where the animal is detected by an animal detection system and drivers are alerted of animals on or near the road.

At-grade fauna passages combine three main components:


 An opening in the fence, constructed to guide animals over the road.

An animal detection system.


A system for alerting drivers of the presence of animals

A red deer detected by the animal detection system. Photo: Swedish Transport Administration.

At-grade fauna passages have been built in several countries, but so far in a lower number compared to fauna bridges and fauna underpasses. The results from available studies are contradictory. Under what specific circumstances may this this type of wildlife passage be made functional for wildlife and drivers? The performance of at-grade fauna passages depends on both animal and human behavior and must be measured in terms of both wildlife connectivity and traffic safety. Above that, there is a technical component that communicates the presence of wildlife to the driver. Thus, several questions remain to be answered. To what degree does the functionality depend on technical details of the different components in the system? How should the driver be informed about the detected animal?

Despite the uncertainties, for economic reasons there is a big interest in constructing at-grade fauna passages, and if made functional they can be used on many roads with low to intermediate traffic flow. Therefore, it is crucial that the performance of new at-grade fauna passages are monitored and that the results are published.

The Transport Administration is in the process of developing a technical platform with products within their framework agreement as well as guidelines and routines for construction and maintenance. The goal is to use a common technical platform with equal technical components in order to make it easier for the road construction projects to construct new sites in the future. So far, two fauna passages with animal detection system have been constructed in Sweden, two more are under construction and planning is ongoing for several more sites in the coming years.

A red deer detected by the animal detection system. Photo: Swedish Transport Administration.


In this subproject we are monitoring the performance of at-grade fauna passages in terms of wildlife use and connectivity between roadsides, and effect on wildlife accidents and driver behavior.

Field methods include studies of animal movements and behavior near and through the crossing (photo traps and filmed sequences from heat cameras), and the effect of the animal warning system on vehicle speed.



This subproject gives insights in the efficacy of level crossings in connecting wildlife between roadsides and in decreasing the number of wildlife accident. Efficacy is separated between species and categories of animals (age and gender) to put light on population level impacts.

The results will contribute to cost-efficiency comparisons between level crossings and over-/underpasses. 

Study sites

Four at-grade fauna passages are studied during 2019-2022:

Sjödiken, road 108, north of Svedala

Detection and warning system from November 2019.

Koberg, at national road 42

Opened for animals from December 2019, but no detection or warning system until fall 2022?

Holmgärdet, at national road 42

Opened for animals from July 2020, but no detection or warning system until 2022?

Haraldsmåla, at motorway E22

Existing detection and warning system.

Site 1: Sjödiken

The animal detection and warning system supplied by the Transport Administration consists of three IR cameras mounted on a 6 m high mast. The system produces thermal imaging videos which cover animal movements across the whole passage. Thus, we are following animals during the whole crossing process, including the most important stage, namely when animals cross the road surface where interactions with vehicles can occur. Milestone (www.milestonesys.com) is the technical platform used for video analysis and activation of the animal warning system. Data are retrieved by a remote connection to the site where the alarms are logged and can be viewed.

Several research questions are explored, among those:


How does the presence of traffic affect the crossing success of an individual (individual level)?

  • Does the traffic volume affect crossing success?
  • Does the traffic volume influence the time it takes for an individual to cross?
  • Does the presence of traffic influence the number of attempts to cross?

How does the presence of traffic affect the crossing rate of a species (event level)?

  • Does the traffic volume influence the likelihood for ungulates to approach the passage?
  • Does group size change or influence the crossing success? Is there a leader/follower effect?
  • Is the activity at the passage influenced by time of day or season?
  • Does the direction of crossing change between seasons/throughout the year?

    The technical functionality of the detection and warning system used at Sjödiken is evaluated by the Transport Administration in a separate project.

      Site 2-4: Koberg, Holmgärdet and Haraldsmåla

      Autocameras (standard trail cameras) are used at these four sites to monitor animal use of the at-grade fauna passages and its nearest surroundings. Data are retrieved from monitoring studies conducted within the respective investment project.

      Data are used to compare ungulate use of at-grade fauna passages with fauna bridges and fauna underpasses.

      The results will be summarized in a report for practitioners, where the international knowledge level regarding efficiency of level crossings will be described and best recommendations for construction will be given. In addition, the goal is to publish the results scientifically.


      A moose detected by the autocameras at Koberg. Photo: Swedish Transport Administration.

      Contact for the subproject

      Mattias Olsson

      +46 (0) 739-47 11 47