Does Highway Safety Signage Actually Reduce Car Crashes?

A new study suggests that some measures intended to reduce traffic accidents may have the counterintuitive effect of increasing them. According to a recent report by the Los Angeles Times, researchers at the University of Minnesota and the University of Toronto looked at the impact of highway safety signage in Texas—specifically, signs displayed every January notifying drivers of the “annual highway death tolls” in the state. What they found is that drivers who passed these digital signs “actually 4.5% more likely to get into an accident over the next 10 kilometres… than drivers unburdened by the information.” In fact, it turned out that the signs may have “directly contributed” to as many as 2,600 more crashes per year, as well as 16 more fatalities and $377 million in costs.

The study, published in Science, consisted of an analysis of 30 months of crash data before Texas launched the signage program, plus five years of crash data after the program went into effect. “They found there were more collisions in weeks when death count messages ran,” explained the LA Times, “with the greatest concentration of accidents in the 10 kilometres immediately following the signs.” The majority of the crashes involved multiple vehicles and situations where drivers had “additional demands” on their attention, like “complicated interchanges” or traffic. 

According to the study’s authors, these results suggest that the signage had the intended effect of drawing drivers’ attention, but the unintended effect of redirecting that attention from where it was needed—the road. Dr Donald Redelmeier, a professor at the University of Toronto, compared this effect to one described in a 2017 study he conducted, which found an increase in deadly motorcycle crashes during full moons—and an even higher increase “during supermoon events.”

Because the human brain is wired to direct its attention toward “things that are large, bright and unexpected,” such visual stimuli can prove deadly when people are travelling on highways. “We did not evolve to travel at 70 or 80 miles per hour. It’s not the way our brains are designed,” Redelmeier told the LA Times. “One or two seconds of inattention can make all the difference in the world when you’re driving a motor vehicle.”

The study’s authors reportedly brought their findings to transportation authorities in states with signage programs like the one in Texas, but they were met largely with dismissal. “We appreciate any focus on safety and the critical need to inspire drivers to make the best decisions behind the wheel,” said the Texas Department of Transportation in a statement. “In relation to this particular study, there are too many unknowns to draw any firm conclusions.”

More information on the effects of safety signage on car crashes is available via the Los Angeles Times and Science.

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