You might expect that a dark road ahead would prompt motorists to slow down, but a collaborative study led by researchers at the University of St Gallen has reached the opposite conclusion. The researchers found that motorists were significantly more likely to break the speed limit when the surroundings were dark, and to react to conditions of lower light by increasing their driving speed. They observed this correlation even when other factors like traffic and the time of day were taken into account. The study, published in the open-access scientific journal PLOS One, is based on data gathered by tracking 1.2 million vehicle movements in the city of Zurich. The researchers attribute their finding to a distortion in drivers’ perception of illuminance, which relates to the amount of light energy striking a surface: when the light is low, we tend to think we are moving more slowly than we really are, and to accelerate in response. This distortion could be due in part to a ...
