5.3.2. Warning signs activated by Animal Detection Systems (ADS)

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Last update: June 2023

Warning signs associated with animal detection systems (ADS) are devices which include sensors to detect animals of different size and activate warning signs to drivers. ADS may also trigger deterrents to scare away animals when vehicles approach and are described in Section 5.4 – Wildlife deterrents. They can only be used on relatively short road sections such as hotspots of animal-vehicle collisions or fence openings.

  • ADS require very particular road verge features and must be frequently checked and maintained, as many factors such as growing vegetation can affect their functionality (see Chapter 7 – Maintenance).
  • ADS may rely on either active light barriers, passive infrared sensors, thermal cameras or radars to detect wildlife movements close to infrastructure (Figure 5.3.2). The power supply is provided by a battery and a small built-in solar module.
  • Where ADS are installed they activate warning signs or panels informing drivers that when a flashing light or message appears it means an immediate collision risk because an animal is close to the road and could cross at any moment. It is recommended that a speed reduction sign accompanies the warning.
  • Wildlife warning devices with ADS are being improved to reduce false positives (activations not caused by the presence of an animal) with a corresponding increase in reliability.
Figure 5.3.2 – Wildlife warning including animal detection system (ADS, movement and infrared sensors to detect the approach of an animal) connected to warning signs that are activated and flash to alert drivers when an animal is close to the road (Photo by: WLS.CH).

Animal detection systems can also be combined with a doppler radar that detects approaching vehicles and their speed to trigger light or noise deterrents that are intended to keep animals off the road. A driver warning may be activated when an animal is detected, and if the speed of the approaching vehicle is higher than a given threshold. Messages such as ‘Animal on the Road’ or ‘Slow down’ could be activated. Optionally they can be fitted with animal deterring sounds or signals (Figure 5.3.3). Similar systems are also being tested to deter ungulates on train lines. Studies have demonstrated an increased effectiveness when sounds are used that animals associate with a real danger, such as human voices or dogs barking (see Section 5.4 – Wildlife deterrents).

Figure 5.3.3 – Wildlife warning sign including an animal detection system (ADS, a thermal camera), a doppler radar sensor to detect vehicle speed and an acoustic deterrent to wildlife. When an animal is detected close to the road the warning sign is activated and, if the car is travelling faster than a fixed threshold, the acoustic deterrent also activates (Source: LIFE SAFE-CROSSING; Photos by: S. Ricci).

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