Public Policy Without Behavioral Science is Dangerous

Imagine you’re driving along the highway, and see an electric sign saying “79 traffic deaths this year.” Would this make you less likely to crash your car shortly after seeing the sign? Perhaps you think it would have no effect? 

Neither is true. According to a recent peer-reviewed study¹ in the journal Science, one of the world’s top academic publications, you would be more likely to crash, not less. Talk about unintended consequences!

Where this road safety campaign went off course

The study examined seven years of data from 880 electric highway signs, which showed the number of deaths so far this year for one week each month as part of a safety campaign. The researchers found that the number of crashes increased by 1.52% within three miles of the signs on these safety campaign weeks compared to the other weeks of the month when the signs did not show fatality information.

That’s about the same impact as raising the speed limit by four miles or decreasing the number of highway troopers by 10%. The scientists calculated that the social costs of such fatality messages amount to $377 million per year, with 2,600 additional crashes and 16 deaths.

The cause? Distracted driving.² These “in-your-face” messages, the study finds, grab your attention and undermine your driving — the same reason you shouldn’t text and drive.

Supporting their hypothesis, the scientists discovered that the increase in crashes is higher when the reported deaths are higher. Thus, later in the year as the number of reported deaths on the sign goes up, so does the percentage of crashes. And it’s not the weather: the effect of showing the fatality messages decreased by 11% between January and February, as the displayed number of deaths resets for the year. They also uncovered that the increase in crashes is largest in more complex road segments, which require more focus from the driver. 

Their research also aligns with other studies. One³ proved that increasing people’s anxiety causes them to drive worse. Another⁴ showed drivers fatality messages in a laboratory setting and determined that doing so increased cognitive load, making them distracted drivers.

If the authorities actually paid attention to cognitive science research, they would never have launched these fatality message advertisements. Instead, they relied on armchair psychology and followed their gut intuitions on what should work, rather than measuring what does work.⁵ The result was what scholars call a boomerang effect,⁶ meaning when an intervention produces an effect opposite to that intended.