Effect of Task and Eccentricity of the Target on Detection Thresholds in Mesopic Vision: Implications for Road Lighting

Abstract

The aim of this work is to assess how adding a driving-related task affects the detection of objects in peripheral vision, under mesopic conditions. The main index used to assess the quality of road lighting installations refers to simple detection tasks in foveal vision, which raises methodological and practical questions. The experimental design consisted of a three-phase experiment. In the first phase, two groups (control and experimental) performed a peripheral detection task (simple task). Based on these results an individual detection threshold was computed for each participant and eccentricity. A tracking task was performed in Phase 2 for both groups (steering a tracking target along a circuit, on a screen). In the third phase, the control group performed the same task as in Phase 2. The experimental group performed a double task, with a tracking (primary) task and a peripheral detection (secondary) task. The data show an effect of the tracking task and eccentricity on peripheral event detection. The tracking task caused detection performance to decrease from 84.2% to 67.5%, p < .001. The small target visibility model used in road lighting may be improved, taking into account the effects of task and eccentricity on target detection. This study supports improved roadway lighting design by guiding consideration of sign eccentricity and task load.