Contact analogue head-up displays (HUDs) showing enhanced images of the forward road scene are currently under development for use under adverse conditions. These can present a driver with a 2-dimensional image at a fixed focal distance that overlays the forward road scene. A key driving task mediated by such an arrangement is the estimation of speed and distance. The present laboratory experiment examined issues of distance estimation arising from the use of a 2-D, fixed focal plane HUD image presented via a free-standing HUD unit. Subjects were presented with a moving object and required to stop it adjacent to a stationary object along its path. The arrangement was viewed directly or through the HUD unit. The HUD image was presented at two focal distances (2.5m and 12.5m). Errors in distance judgement were contrasted across conditions and systematic errors were examined. Experimental hypotheses suggested an interaction between the focal plane at which the objects were imaged and estimates of their relative distances. Statistically significant effects in the hypothesised directions were observed.
Abstract