Thanks for the info Rob! Lot´s of research going on in this field. After decades of trying to warn the animals (first red reflectors which are not working with ungulates and now blue reflectors and sound) the two main approaches now are understanding where and when animals cross the streets (big data, telemtry data from GPS collared animals, remote sensing phenology and landscape structure) and warning the drivers (https://animot.eu/en/). Slowing down traffic via google maps or apple maps at the right time and place might be the most effectiv way of preventing wildlife collisions.

Benten, Anke, et al. "Wildlife warning reflectors do not mitigate wildlife–vehicle collisions on roads." Accident Analysis & Prevention 120 (2018): 64-73.

Brieger, Falko, et al. "Do roe deer react to wildlife warning reflectors? A test combining a controlled experiment with field observations." European Journal of Wildlife Research 63 (2017): 1-11.

Kämmerle, Jim-Lino, et al. "Temporal patterns in road crossing behaviour in roe deer (Capreolus capreolus) at sites with wildlife warning reflectors." PloS one 12.9 (2017): e0184761.

Brieger, Falko, et al. "Behavioural reactions to oncoming vehicles as a crucial aspect of wildlife-vehicle collision risk in three common wildlife species." Accident Analysis & Prevention 168 (2022): 106564.

Brieger, Falko, et al. "Effectiveness of light-reflecting devices: A systematic reanalysis of animal-vehicle collision data." Accident Analysis & Prevention 97 (2016): 242-260.

I did work with this system: lights and sounds activated by the sound of the car or train and/or the light of the headlights. The signal is then forwarded to the next sensor/sound transmitter:

Greetings from Austria to Australia (there are no roos in Austria ;-), 

Robin

The idea is not new. It has been tested twenty years ago:

short english summary: 

https://www.fva-bw.de/fileadmin/scripts/forschung/wg/081014wildwarn_en.pdf