Detection thresholds in car following situations and peripheral vision: implications for positioning of visually demanding in-car displays

This on-road study examined the effect of the positioning of an attentionally demanding in-car task on the driver's ability to detect the approach of a decelerating car ahead. Twelve participants aged between 19 and 27 years with an average of 18 170 km life-time driving experience drove 20 and 40 m behind a vehicle which decelerated from 50 km/h at ~0.7 m/s2 without braking. Detection thresholds for nine locations of a LED display were compared with thresholds when focusing on the car ahead. A strong inverse relationship was found between time-to-collision (TTC) and eccentricity of the task to the normal line of sight, with TTC decreasing from 6 to 8 s at 0° eccentricity to 4 s at 90°. The results suggest that there are optimal locations, in terms of detecting the deceleration of a car ahead, for positioning attentionally demanding in-car devices, and that there are some differences in detection thresholds for similar eccentricities in the vertical and horizontal peripheries of the eye.