Attention-capturing properties of high frequency luminance flicker: Implications for brake light conspicuity

In two experiments, the authors studied the effect of high frequency luminance flicker on reaction time in a simulated driving task. In Experiment 1, 24 research participants performing a primary simulated driving task were required to apply the brake pedal as quickly as possible following the activation of a red light somewhere in their field of vision. The red lights were displayed in one of two ways, (a) with 20 Hz luminance flicker and (b) continuous (no flicker), and presented at three eccentricities, 10°, 45° and 80°. Results showed that the light with 20 Hz flicker was more attention-capturing than the continuous light, but that the effect of 20 Hz flicker on reaction time was not influenced by eccentricity of presentation. The second experiment was identical to the first except that the primary simulated driving task was considerably more attention demanding. Under this higher workload, the light with 20 Hz flicker again proved to be more attention-capturing than the continuous light, and to a greater extent than in Experiment 1. In Experiment 2, there also appeared to be tendency for the light with 20 Hz flicker to be more effective at greater eccentricities. Implications for brake light conspicuity and rear-end collision avoidance are discussed.