Are digital billboards more dangerous for road users than paper ones?

The answer is simple: yes.

However, applications to replace a paper billboard with a digital one regularly claim that “the replacement will be like-for-like” or that “there is no evidence that a digital billboard is more distracting than a paper advert”. The goal of this blog post is to debunk this myth.

What does research say?

With ads being so omnipresent all over our roads, you would expect that there is a lot of research to guide policy makers in their decisions. It is actually quite hard to find research papers that look into the direct effects of digital outdoors advertising, in particular because research struggles to keep up with the new, ever-more aggressive marketing strategies devised by big corporation.

This being said, we did find a few good, recent journal articles that study the impact of digital billboards on road users in comparison to static ones. The main conclusion is that the most recent research suggests there is a direct link between roadside advertisement and car crashes (Herrstedt et al., 2013), and that is especially the case for digital billboards (Oviedo-Trespalacios et al., 2019). What most studies have found is that drivers tend to look more frequently and for longer periods at digital billboards (Beijer et al., 2013, Decker et al., 2015). The main two reasons that make digital billboards more distracting are their brightness (Zalesinska, 2018) and the fast changing images, for example when transitioning from an ad to the next (Belyusar et al., 2016, Roberts, 2013).

One thing that most articles agreed on is the need for more research. These articles often provide average data, however accidents are not an ‘average’ occurrence but a rare one, and generally happen because of a combination of events. Because of that, it is important to look at the impact of a billboard in a situation already prone to causing an accident (Decker et al, 2015), which will likely show a much bigger impact.

The difference between causing a car crash and being distracting

Importantly, as accidents happen rarely by nature (in statistics we would call them outliers or extreme events), it is hard to gather statistically significant data about whether car crashes increase with the installation of a new billboard (although this paper does present such data). And it is also hard to attribute an accident to a single cause, which again is used as an argument to say “the billboard had nothing to do with it”.

And obviously, researchers cannot carry out experiments involving car accidents to test a hypothesis, but what they can do is to measure the level of distraction of a road user facing a digital billboard vs a paper one. And there, as we saw above, the scientific consensus is clear: digital billboards distract drivers from the road more than paper ones. So when we know that 40% of car accidents in the UK occur because the “driver/rider failed to look properly”, the presence of digital billboards clearly poses a threat to road users.

So when applicants claim there is no evidence that digital billboards increase car crashes (but not mentioning distraction), they are just ignoring the data and playing on words to confuse the general public. Sounds familiar? Well, probably because the tobacco and the fossil fuel industry have been using the same misinformation techniques for decades.

Where does this leave us?

Such evidence helps us make arguments against digital billboards when we object to ad applications on the grounds of road safety. It is always a good idea to include a few references to such research (or link to summaries like this blog posts) when crafting your objections.

It also helps to be aware of the requirements associated with digital billboards and when they are breached. For example, digital billboards often display moving images even though this is against regulations (this was filmed in Headingley, and this in Kirkstall). This clearly makes them even more dangerous for road users than the terms of the applications imply.

Last but not least, going digital opens up more avenues for advertisers to induce demand in ways that threatens personal agency and public choice, for example, through personalised messaging. This makes them much more interesting and profitable for advertisers. So unless we push back, we are likely to see more and more of them in our cities.

On this note, let’s push back!

Appendix: selected quotes from scientific articles

Oviedo-Trespalacios et al., 2019
– there is an emerging trend in the literature suggesting that roadside advertising can increase crash risk, particularly for those signs that have the capacity to frequently change (often referred to as digital billboards)
– the degree of changeability in the information conveyed by the roadside advertising signs appears to have a persistent adverse effect on driver behaviour
– it has been demonstrated that changeable (i.e., digital with multiple advertising signs) roadside advertising signs represent a greater distraction to drivers than static (i.e., single advertising sign) roadside advertising signs
– many researchers have claimed that digital roadside advertising signs present a higher safety risk for the general public as the changes in luminance are more likely to catch a driver’s attention than traditional static signs
– digital roadside advertising signs also hold a driver’s attention for longer than standard floodlit signs
– The researchers found that average glance duration at LED signs was longer when compared to other types of objects (i.e. anything the driver looked at for more than one second, including static, non-LED advertisements

Beijer et al., 2004: The number of glances was significantly lower for passive signs (0.64 glances per subject per sign) than for active signs (greater than 1.31 glances per subject per sign). The number of long glances was also greater for active signs than for passive signs.

Decker et al., 2015:
– active billboards drew more glances and more long glances (≥0.75 s, ≥2.0 s) than passive billboards but did not attract a longer average glance, and that there was large variability among individual billboards within categories (e.g., active vs. passive).
– Future research should emphasize the tails of the distribution in addition to average cases, in terms of both the analysis of visual behavior and the complexity of driving tasks.

Belyusar et al., 2016: Results show a significant shift in the number and length of glances toward the billboards and an increased percentage of time glancing off road in their presence. Findings were particularly evident at the time the billboards transitioned between advertisements.

Roberts, 2013: it is likely that the movement or changes in luminance created by digital displays will involuntarily capture attention and that particularly salient emotional and engaging material will recruit attention to the detriment of driving performance, particularly in inexperienced drivers.

Herrstedt et al., 2013: The overall results of the empirical studies show that advertising signs do affect driver attention to the extent that road safety is compromised.”

Full references

Beijer, D., Smiley, A., Eizenman, M., 2004. Observed Driver Glance Behavior at Roadside Advertising Signs. Transportation Research Record 1899, 96–103. https://doi.org/10.3141/1899-13

Belyusar, D., Reimer, B., Mehler, B., Coughlin, J.F., 2016. A field study on the effects of digital billboards on glance behavior during highway driving. Accident Analysis & Prevention 88, 88–96. https://doi.org/10.1016/j.aap.2015.12.014

Decker, J.S., Stannard, S.J., McManus, B., Wittig, S.M.O., Sisiopiku, V.P., Stavrinos, D., 2015. The Impact of Billboards on Driver Visual Behavior: A Systematic Literature Review. Traffic Injury Prevention 16, 234–239. https://doi.org/10.1080/15389588.2014.936407

Herrstedt, L., Greibe, P., Andersson, P.K., 2013. Driver attention is captured by roadside advertising signs. Presented at the 16th International Conference Road Safety on Four Continents. Beijing, China (RS4C 2013). 15-17 May 2013, Statens väg- och transportforskningsinstitut.

Oviedo-Trespalacios, O., Truelove, V., Watson, B., Hinton, J.A., 2019. The impact of road advertising signs on driver behaviour and implications for road safety: A critical systematic review. Transportation Research Part A: Policy and Practice 122, 85–98. https://doi.org/10.1016/j.tra.2019.01.012

Roberts, P., 2013. Designing evidence-based guidelines for the safe use of digital billboard installations : Experience and results from Australia. Presented at the 16th International Conference Road Safety on Four Continents. Beijing, China (RS4C 2013). 15-17 May 2013, Statens väg- och transportforskningsinstitut.

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