RATIONALE. Wildlife warning signs
Wildlife traffic signs are one of the most used mitigation measures, aiming to alert drivers about the potential presence of wild animals on the roads and thereby reducing the risk for AVC. A literature review of the topic is provided by Huijser et al. (2015). Standard (static) wildlife warning signs are more commonly used, although they are generally less effective as drivers become habituated and tend to ignore them (Found & Boyce, 2011; Bullock et al., 2011; Huijser et al., 2015; van der Grift et al., 2017). Enhanced wildlife warning signs, which are bigger, transmit more specific messages, or include eye-catching details, may initially be more noticeable to drivers, but suffer from the same habituation effect as standard signs (Huijser et al., 2015).
Temporary wildlife warning signs are more specific as to where and when AVC risks are elevated, which makes them more reliable for drivers and hence more effective (Sullivan et al., 2004; Gagnon et al., 2010; Huijser et al., 2015). Active warning signs triggered by Animal Detection Systems (ADS) display even more acute information about the immediate accident risk. Active devices are more effective than temporary and standard warning signs, especially if combined with temporary speed limitations.
Both static, temporary and active warning signs can be applied to roads with low to intermediate traffic volumes and low to intermediate speeds, where drivers are able to reduce speed suddenly or even stop vehicles to avoid animals (Bhardwaj et al., 2022). On motorways with high speed and busy traffic, wildlife warning signs may be pointless or even hazardous. Here, only the physical separation of wildlife and traffic by fences and wildlife passages is recommended from a traffic safety perspective (Huijser et al., 2015; van der Grift et al., 2017).
Standard wildlife traffic signage is placed in areas where collisions often occur and consequences for human safety are significant. Studies indicate that there is no corresponding reduction in accidents involving wildlife, so these standard signs do little more than provide a legal protection to road operators (see Rationale box. Wildlife warning signs). Road users quickly get used to such signs, especially if they are present all year round and if the driver uses that stretch of road frequently (Figure 5.3.1A). Drivers ignore permanent signs probably because the sign doesn’t often correspond with real presence of an animal close to the road.
The combination of a wildlife warning sign with a speed limit is slightly more effective. The effectiveness is further enhanced if signs are marked with flashing lights or a flashing speed limit sign, lit only during periods of high target species activity.
Temporary warning signs, activated only during critical periods of the year, in locations with high risk of collision, have shown higher effectiveness (in terms of AVC reduction) than permanently installed signs. These temporary signs could be reinforced with flashing lights or reflective panels (Figure 5.3.1B).