U.S. traffic fatalities started rising 2 years ago after several years of declines. Psychologists around the world are looking for ways to improve traffic safety.

Psychologists have found both perceptual and cognitive biases that nudge people toward unsafe speeds, said Ola Svenson, PhD, a psychologist and head of the Risk Analysis, Social and Decision Research Unit at Stockholm University in Sweden. Drivers overestimate how much time they’ll save by speeding and grossly underestimate the increased accident risk at higher speeds (Applied Cognitive Psychology, Vol. 23, No. 4, 2009). They also underestimate how long it takes to stop at high speeds. In one study, Svenson and his team presented participants a scenario in which a child runs in front of a car driving 18 mph. At that speed, the driver can slam on the brakes and just avoid hitting the child. What then, the participants were asked, would happen if the driver were going 25 mph in this scenario?

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