Animal Detection and Driver Warning Systems – a potential solution for wildlife-vehicle collisions & loss of landscape connectivity on secondary roads
Written by Manisha Bhardwaj
Chair of Wildlife Ecology and Management, University of Freiburg, Germany
December 10th, 2024
Summary
Wildlife-vehicle collisions (WVCs), and loss of landscape connectivity are two of the most prominent negative impacts of roads and railways on wildlife. Wildlife crossing structures (i.e., over- and underpasses) and fencing are commonly implemented to reduce WVCs and provide safe crossing opportunities for wildlife.
Due to costs and technical constraints, fencing and crossing structures tends to be prioritized where they benefit traffic-safety the most, i.e., along primary roads with high speed and high-volume traffic. This often leaves secondary roads unmitigated, despite the fact that WVCs occur frequently on such roads. Alternative mitigation options are urgently needed for secondary roads!
Animal Detection and Driver Warning Systems
Animal Detection and Driver Warning Systems (ADDWS) may be an alternative solution to over- or underpass. ADDWS consist of four components (Figure. 1):
Fencing, to reduce the access of wildlife to the road or railway.
The fauna passage, to provide a safe crossing opportunity for wildlife. In ADDWS, the fauna passage is an at-grade crossing, a designated opening in the fencing where wildlife can cross.
A fauna detection system, which detects animals as they approach and are within the fauna passage.
A system to alert drivers to the presence of animals near or in the fauna passage, usually through variable-message signage.
ADDWS differ from crossing structures because they do not physically separate animals from traffic, and also rely on drivers to respond to the warnings in order to avoid collisions. Thus, the success of ADDWS depends on:
The reliability of the animal detection and signage system
The response of drivers to the warnings.
How wildlife approach and cross the road .
In this pilot study, we focussed on how wildlife approach and cross the road.
Figure 1. Top: Location of the at-grade fauna passage in in Skåne County, southern Sweden. Road 108 is shown in the black box, and the fauna passage is in the southern parts of this road. The three unmitigated reference road sections are shown in blue ovals (Basemap: OpenStreetMaps). The schematic below the localized map shows a technical drawing of the at-grade fauna passage. Bottom left: Screenshot from a video of roe deer within the fauna passage. Bottom right: The warning sign displayed to drivers when an animal was within the at-grade fauna passage.
Road 108 in southern Sweden
We conducted this pilot at one ADDWS along a 5.2 km segment of Road 108 in southern Sweden (Figure 1). Road 108 has one traffic-lane in each direction, a speed limit of 80 km/h, and a daily traffic volume of 6000 vehicles/day. WVC in this area tend to involve ungulates, such as roe deer, red deer and wild boar.
Road 108 is fenced for its entire length, except for at the 30 m wide fauna passage opening. The fauna detection system uses a series of heat-, infrared, and motion triggered cameras to detect wildlife in the roadside verge on each side of the road (“i.e. the detection zone”). The cameras continuously record the site and track the movement of animals from one verge to the other. When an animal is detected, a variable message sign on each side of the crossing is activated automatically, and a conventional “warning of moose” graphic sign is displayed until 60 seconds after the last animal is detected (Figure 1).
The fencing and ADDWS was built in 2019, and activated in January 2020. We collected 91 videos of roe deer, 99 videos of red deer, and 136 videos of wild boar at this site between 24 January 2020 and 24 January 2021. Using the videos, we explored how wildlife cross roads and respond to traffic, and the impact this has on the risk of potential collision (video example, Figure 2).
In addition to wildlife behaviour, we investigated if the ADDWS reduced the number of WVC by comparing the number of WVC at Road 108 with three similar unfenced roads nearby (Figure 1).
We explored WVC data collected between 1 January 2015 to 30 December 2021, covering 1307 days before, 424 days during, and 822 days after the ADDWS site was constructed.
What behaviours did we detect using the ADDWS?
Roe deer, red deer and wild boar had similar behaviours. They spent a majority of their time in the roadside verge grazing on grass, rather than attempting to cross the road. Roe deer spent the longest amount of time there of the three species. When either species attempted to cross the road, they were fast and direct, however if vehicles were present, individuals tended to hesitate or avoid crossing. When vehicles passed on the road, the time roe deer, red deer and wild boar spent in the verge tended to increase, and they crossed the road less.
Figure 2. Wild boar quickly crossing through the at-grade fauna passage as a vehicle approaches. Video: Trafikverket
So, how effective can it be?
WVC at the mitigated section of road decreased 66 %, compared to before mitigation (from 0.078 WVC/day to 0.027 WVC/day; Figure 3). Comparatively, there was a relative increase in WVCs at the three unmitigated reference road segments (reference 1: 0.047 WVC/day to 0.052 WVC/day; reference 2: 0.130 WVC/day to 0.141 WVC/day; reference 3: 0.142 WVC/day to 0.139 WVC/day; Figure 3). Importantly, we only recorded 3 WVC during the 12 months of video data (all with wild boar), compared to an average of 30 collisions/year prior to installing the ADDWS.
Figure 3. The number of wildlife vehicle collisions, summarized per quarter (i.e., Q1: January – March; Q2: April – June; Q3: July – September; Q4: October – December), from 2015 – 2021. The solid black line represents the road segment corresponding to the at-grade fauna passage. The dashed grey lines represent the three unmitigated reference sites that are similar in length, traffic volume and posted speed limit.
Animal Detection and Driver Warnings can be effective, but more studies needed
Landscape connectivity – i.e., safe, unhindered movement across the landscape - may be best achieved when many and different crossing opportunities are available across the whole road network, rather than fewer opportunities on major roads. Over- and underpasses are effective for many species because they separate fauna from traffic. Additionally, ADDWS may provide an alternative solution to improving the permeability of road networks for wildlife in areas where over- and underpasses are not feasible, but animals can safely cross at-grade while drivers are warned of the risk. From the results of this pilot study, we suggest that fences and ADDWS can reduce collisions and maintain connectivity over secondary roads for large ungulates. In order to be certain, further study is necessary.
Consideration for development and design
We recommend a target-oriented approach for both the ecological evaluation and technical development of this type of fauna passage. It is important that the functional requirements and goal formulations are defined and tested.
For example, the goal for this ADDWS in Sweden is to provide safe passage for both fauna and drivers. Specifically, the goals we set are:
>80 % reduction in WVC at the mitigated road section - our pilot achieved a 66 % reduction.
<0.3 % of the animals that visit the at grade fauna passage are involved in traffic accidents – our pilot achieved 0.5 %.
>70 % of visiting animals cross through the fauna passage – our pilot achieved 75 % for all species combined.
<2 % of the animals that visit an at grade fauna passage enter the fenced infrastructure – our pilot achieved 2.6%.
ADDWS have the potential to improve wildlife connectivity, motorist safety and reduce fauna mortality and rigorous trials and should be implemented globally to further test and refine the approach.
There is an Infrastructure and Ecology Network of Europe (IENE) Working Group on Animal Detection and Driver Warning System. The working group is designed to bring together those working with, or interested in working with, solutions as presented in this blog. For more information, please contact Manisha Bhardwaj, manisha.bhardwaj@live.ca
Author information
Manisha Bhardwaj
Chair of Wildlife Ecology and Management, University of Freiburg, Germany
Source citation
Bhardwaj M, Erixon F, Holmberg I, Seiler A, Håkansson E, Elfström M and Olsson M (2022). Ungulate use of an at-grade fauna passage and roadside animal detection system: A pilot study from Southern Sweden. Front. Environ. Sci. 10:991551. doi: 10.3389/fenvs.2022.991551
Editor:
Julia Kintsch
Cite this summary:
Bhardwaj, M. (2024). Animal Detection and Driver Warning Systems - a potential solution for wildlife-vehicle collisions & loss of landscape connectivity on secondary roads. Edited by Kintsch, J. TransportEcology.info, Accessed at: https://transportecology.info/research/effectivness-addws-in-sweden