Abstract
Previous studies have shown that people rely mainly on splay angle (the optical angle of the lane markers with respect to the vertical in the image plane) for lane keeping during driving (e.g., Beall & Loomis, Perception, 1996). Here we investigate whether optic flow and bearing also contribute to the control of lane keeping. The display (110° H × 94° V) simulated an observer steering a vehicle down a straight path at 3 m/s under three conditions: (a) an empty ground with lane markers providing bearing and splay angle information; (b) a random-dot ground with lane markers providing bearing, splay angle, and sparse optic flow information, and (c) a textured ground with lane markers providing bearing, splay angle, and dense optic flow information. Participants used a joystick to control the vehicle's lateral velocity to stay at the center of the lane while the vehicle's lateral position was perturbed by the sum of seven non-harmonic sinusoids (0.1 to 2.19 Hz). For 11 participants (9 na?ve), the vehicle's lateral deviation from the center of the lane, indicated by the RMS error, was larger for the empty ground (mean±SE: 0.39±0.02 m) than for the random-dot and the textured ground display (0.37±0.02 m in both cases), indicating the influence of optic flow on lane keeping. We then varied the optical gain of bearing in the display by providing lane markers (3.1± V) at three distances (3.2 m, 7.8 m, & 22.2 m). For eight participants (7 naïve), the RMS error increased with the distance for the empty ground but not for the random-dot or the textured ground display, indicating that bearing information helps lane keeping in the absence of optic flow information. We conclude that optic flow, bearing, and splay angle all contribute to accurate lane keeping.
Hong Kong Research Grant Council, HKU 7471//06H