5.6.6 CUESTIONARIO JUICIO DE EXPERTO

This paper is discussed in Section 3, “Industry sponsored research.”

Shinar, 2007

In his recently published, comprehensive book on the human factors of traffic safety, Shinar devotes a chapter to distraction, its definitions, causes, and effects, and a section within this chapter on distraction from road signs and billboards.

The author poses a paradox that has confronted researchers in this field for many years. Because roadside commercial billboards, particularly the latest digital billboards, are specifically designed to attract a driver’s attention (and billboard owners and operators tout their success at doing so in their promotions to potential customers), we would expect them to be a significant source of distraction. Indeed, as discussed elsewhere in the present report, numerous studies have shown that drivers do direct their gaze to billboards as they drive. Yet several studies have demonstrated that despite drivers’ glances toward billboards, there has been little observed adverse impact on driving performance. In an effort to better understand this paradox, Shinar and his colleagues conducted an on-road study using 16 experienced drivers and an instrumented vehicle. The route took the participants past a large, attention-getting billboard in one direction and then followed the same roads in the opposite direction from which the billboard was not visible. A camera hidden below the vehicle’s rear-view mirror recorded the

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only 10% of the time when the billboard was not visible to them. Drivers’ time spent looking forward at the road and traffic was effectively the same regardless of whether or not the billboard was visible. Shinar believes that the billboard attracted the drivers’ spare attentional capacity that might otherwise have been spent looking at other objects equally irrelevant to the driving task. He concludes: “Thus, drivers were able to allocate a

significant amount of their attention to the sign but they did not do that at the expense of the attention that they allocated to monitoring the road and traffic” (p. 528).

Shinar’s discussion suggests that drivers are willing and able to devote their attention to billboards when their task demands are low, and when the billboard provides greater interest than other roadside objects, but that, as their cognitive demands increase, drivers will devote less attention to these roadside distracters. Other studies, and the billboard industry, have suggested the same thing. And this may well be the case for some drivers, some of the time. But this begs the real question. Because of the considerable expense of new, digital billboards, they tend to be placed only in areas with high traffic volumes. In addition, because advertising space (and, with digital billboards, time) is sold to

advertisers based on the number of eyes that will pass the billboard each hour or each day, such billboards tend to be located where they can be seen by the greatest possible number of drivers. This explains why billboards are often placed near highway

interchanges and along horizontal curves where they can appear directly within the cone of vision of approaching drivers for extended distances. Thus, DBBs tend to be located in areas where task demands are likely to be high, and, billboard owners claim, (and present data to show), they attract the gaze of large numbers of drivers.

Conducting the kind of research that would be necessary to prove that drivers attend to billboards when they have spare capacity, and concentrate on the road when they do not, is a challenge that, to our knowledge, has not yet been undertaken. We do know,

however, that several recent studies (e.g. Smiley, et al. 2005; Lee, et al. 2007; and Chan, et al., 2008) have produced data showing that some drivers attend to billboards for extended glance durations that have been shown, in other studies (e.g. Klauer, et al., 2006a) to be unsafe. To date, however, only the Chan, et al., study controlled for and reported on the task demands that their participants faced while engaging in these glances toward external distracters. Further, we know of only one study (Lee, et al., 2007) that collected data on drivers passing DBBs at night, when such signs can be most

conspicuous (because of their location, size, and brightness), and may be most likely to cause high levels of distraction. Although their data was preliminary and based on only a few participants, Lee and her colleagues showed that DBBs, as might have been

predicted, captured more and longer glances at night than other roadside distracters, and they have suggested that, had a full study (rather than the pilot study that they performed) been conducted, these differences might have reached statistical significance.

Also, we must recognize that not all drivers are willing or able to safely switch their attention from roadside distracters to the driving task itself when needed. In particular, younger drivers, not yet sufficiently skilled to understand risky situations, and older drivers who may be more easily distracted and who are typically poorer than their

younger cohort at quickly shifting attention, may be particularly at risk under such circumstances.

Finally, although accidents are (thankfully) rare events, they are, by definition, unexpected. As Shinar states: “One way to reduce the effort involved in driving, is to estimate the amount of attention that is required and then allocate to the driving a portion of our capacity that is somewhere between the minimum required and the maximum we have. … The problem we encounter in driving is our inability to anticipate many of the rapid changes in the amount required – as when a driver ahead of us suddenly and unexpectedly brakes” (p. 518). It is precisely this difficulty that leads traffic safety experts to be concerned about the compelling power to distract a driver when it is always possible that such distraction cannot be tolerated at the moment it occurs.