Warnings on electronic road signs may do more harm than good.
The message displayed on the electronic board above the American highway emphasizes the number of traffic accident deaths every year, in order to remind people to drive safely. But statisticians warn that there is convincing evidence that these signs actually lead to more accidents.
Although this information is displayed in many states in the United States, Jonathan Hall of the University of Toronto in Canada and colleagues chose to study the traffic accident data in Texas, because the state uses electronic cards to issue death warnings only once a month, which provides sufficient control data for comparison.
The researchers compared the number of car accidents in the first two years and five years after the establishment of the “death sign”. They found that displaying death information increased the number of car accidents on the road 10 kilometers behind the electronic card by 4.5%. Their results show that death information causes another 2600 car accidents and 16 deaths in Texas every year.
Hall attributed this effect to distraction and an increase in the cognitive load of drivers when receiving information. “When you see it, you will think about it, so you won’t step on the brake soon, and these small mistakes may cause a crash once in every 50 times.” “Randomized controlled trials will be perfect evidence and very convincing evidence,” he speculated
He said that the number of deaths displayed on the electronic card will also strengthen its impact, because the larger number is more shocking. In Texas, the number of deaths in February is reset every year, and the team found that traffic accidents in February decreased significantly compared with January.
Hall said his team had written to all states that displayed such warnings and asked them to cooperate with them for further research, but there was little positive response. “If you want to launch a safety campaign, it’s not difficult to say ‘let’s randomly select five weeks from the next six months to show this sign and analyze the accident’. But they didn’t do so because they just assumed that the signs wouldn’t cause harm.” He said.
The researchers reported their findings in the April 22 issue of the journal Science. (Li Muzi)
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