Questions for a TUD expert: Dipl.-Psych. Christoph Schulze from the photometric and visual laboratory at the Chair of Traffic and Transportation Psychology

Wildlife accidents are a significant problem. Established measures (fences and wildlife bridges) are neither possible nor practical where there are wide areas to cover. That is why, in many places, wildlife warning reflectors are used. Although there are some national and many international studies on their impact on accident occurrence – with varying findings – there is still a lack of evidence of their benefits. The underlying technical principle was comprehensively investigated for the first time in the photometric and visual laboratory at the “Friedrich List” Faculty of Transport and Traffic Sciences.

UJ talked to Christoph Schulze from the laboratory. Together with Jens-Ulrich Polster from the Lectureship for Wildlife Ecology and Management (Faculty of Environmental Sciences), he ran a project entitled “Wirkungsweise von Wildwarnern” (“Effectiveness of wildlife warning devices”) for the German Federal Highway Research Institute (BASt).

UJ: Preventing accidents affecting humans and animals is, of course, the most important goal of projects designed to keep wildlife off the roads. Beyond that, is it possible to quantify the economic benefits for motor vehicle insurance companies and owners if we offset the costs of installing wildlife warning reflectors along rural roads? Or in other words: Is the widespread introduction of warning devices really worthwhile, given the relatively low number of wildlife accidents?

Christoph Schulze: The number of wildlife accidents is, unfortunately, considerably higher than sometimes assumed, although we do not know the exact figures. You mentioned vehicle insurance companies. The German Insurance Association (GDV) puts the number of vehicle claims due to wildlife accidents in 2017 at 275,000, with the insurance payouts totaling around 775 million euros.

The DJV (German hunting association) reports about 230,000 cases of what is known in Germany as Fallwild. This category covers animals killed in collisions with motor vehicles as well as animals found dead in the forest with obvious injuries. It only includes the larger species of game: roe deer, wild boar, fallow deer, and red deer.

These figures contrast with a significantly lower number of accidents involving wildlife in the official traffic accident statistics. According to the German Federal Statistical Office, around 2500 accidents involving wildlife and causing personal injury were recorded by the police in Germany in 2017. About 2900 people were injured and ten killed in those accidents. The majority of wildlife accidents, therefore, are not recorded by the police. In many cases, however, hunters are required to come and deal with the – usually dead – animal. Incidentally, this applies not only to road but also to rail transport.

Measures of any kind that lead to a systematic reduction in accidents between motor vehicles and wildlife are therefore being urgently sought. One measure that has been under discussion internationally for some time and has also been used increasingly in Germany in recent years is wildlife warning reflectors.

What is the basic idea behind using wildlife warning reflectors?

Briefly, the idea is to use additional reflections to warn animals or scare them away from approaching motor vehicles. There are a number of elements involved in the process. Firstly, there is the vehicle with its headlights. Headlights must provide the light, although there are significant differences in intensity here that come down to more than just distance. Secondly, there is the wildlife warning reflector itself. For practical reasons, wildlife warning reflectors are usually attached to the back of delineators, which are standard on roads outside built-up areas. Wildlife warning reflectors are designed to redirect light from headlights to the side and toward the wildlife. As we cannot know where the animals are, reflections should ideally cover the entire area to the side of the road. The intended effect is that wildlife see the reflected light and stay off the road. Some wildlife warning reflectors are supposed to reflect only blue light from headlights. This is because blue light is thought by some to have a greater impact on wildlife than other colors of light.

Can we expect wildlife warning reflectors to work in roughly similar ways for different species? Quite apart from the size of the animals, does how an animal sees not differ from species to species?

In fact, we know very little overall about what exactly wild animals see. It is difficult to establish how well they see what they see. After all, the only reason we know so much about human vision is because we can verbalize the effects of different light stimuli or demonstrate those effects in carefully designed experiments. We do not have these options for assessing wild animals. Besides observing behavior, all we can do is therefore examine the sensory organs themselves. Findings on this basis tell us that there are major differences between different species of wildlife. We can therefore reasonably estimate that different animals perceive certain light stimuli very differently. One of the reasons for this may be that the importance of vision itself can vary greatly depending on the species – and is probably often less important to wildlife than it is to us humans. On the other hand, many wild animals have a much more acute sense of smell and hearing than we do.

What exactly did you investigate and how?

We used ten different wildlife warning reflectors to investigate the actual reflections they produce toward the side of the road. Before we can properly discuss possible perceptual or behavioral effects in wildlife, we need data on the actual stimuli. Interestingly, there have to date been no systematic laboratory studies anywhere in the world of how these features act in terms of light.

First, we established the direction and intensity of light reaching the wildlife warning reflector from passing vehicles by setting up a test station that allowed us to record reflection simultaneously for the entire potential range (area along the side of the road). This allowed us not only to determine how well the reflectors caught the light, but also to assess the area across which they distribute it.

We also looked at the reflectors from the perspective of potential wildlife in the area beside the road and at reflections on the wildlife warning reflectors for a 300 m vehicle approach. On this basis, we were able to map the scale and intensity with which light would be reflected toward wildlife and how reflections appear against the background of the road, for example, which is also illuminated. Finally, we investigated the manner and intensity with which light from headlights is reflected in the direction of vehicle traffic.

What were your findings?

First of all, it must be said that there are significant differences between the wildlife warning reflectors in terms of all the characteristics studied. If you take how well they reflect, for example, the better products reflect up to three quarters of the light emitted by headlights – light that is already not particularly powerful – into the area beside the road; other products reflect only two percent.

Distribution also varies considerably, but in the best cases is confined to a few relatively small areas. On average, the reflectors studied emit light into about four percent of the space beside the road; in the best cases, this figure was just over ten percent. In other words, no additional light at all reaches most places where there may be wildlife.

As seen by an animal beside the road, the reflections are, moreover, very small areas of light, in fact usually dots. In no cases will the wildlife warning reflector be visible in its entirety. We were also able to show that there was in most cases surface reflection on tiny parts of the smooth plastic. This means that, regardless of the color of the surfaces, no spectral filter effect can occur and thus no colored reflections are produced. Instead, the reflections are the color of the vehicle headlights.

In short, regardless of their design, wildlife warning reflectors are not a means of creating light signals of relevant intensity and distribution to shine into the areas beside roads.

Who is actually responsible for installing such warning devices along the sides of rural roads (I assume it is rural roads that are most affected) and what would you advise them based on your findings?

Devices are a potential part of road equipment, so it would be the public sector, in other words the federal states and administrative districts in the case of many rural roads, that would be responsible. Until now, these authorities have simply tolerated the installation of wildlife warning reflectors by hunters or forest owners, not least because of the absence of reliable proof of effectiveness; in most cases, they have not installed reflectors themselves.

The question of advice is a more difficult one. The results of the study show it is most unlikely that reflections from wildlife warning reflectors can provide anything more than random, haphazard warnings for wildlife. At the same time, however, there is significant pressure to act in many areas due to the number of accidents involving wildlife, for which there has to date been a lack of suitable widespread measures.

At the moment, therefore, various lines of research in this area are possible. For example, there has yet to be a systematic study of drivers and their ability to reduce wildlife accidents. Sensor technology in vehicles is also an area to be considered. Finally, existing findings suggest that clusters of wildlife accidents in specific places or at specific times in particular are likely to be related to factors other than vehicle traffic, and analyzing and shaping those factors could positively affect road safety.

Christoph Schulze was interviewed by Mathias Bäumel.

This article was published on November 13, 2018, in the 18/2018 Dresden Universitätsjournal. You can download the full issue as a PDF for free here. You can also order the UJ in print or as a PDF from doreen.liesch@tu-dresden.de. More information is available at universitaetsjournal.de.