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When Red Lights Look Yellow, Joanne M. Wood, David A. Atchison, Alex Chaparro

Publications

Purpose. Red signals are typically used to signify danger. This study was conducted to investigate a situation identified by train drivers in which red signals appear yellow when viewed at long distances (∼900 m) through progressive-addition lenses.

Methods. A laboratory study was conducted to investigate the effects of defocus, target size, ambient illumination, and surround characteristics on the extent of the color misperception of train signals by nine visually normal participants. The data from the laboratory study were validated in a field study by measuring the amounts of defocus and the distances at which the misperception of the color of …