Geometric field of view manipulations affect perceived speed in driving simulators

In driving simulators and other virtual reality systems, visual speed is frequently underestimated leading to speed overproduction. This, in turn, may compromise the validity of human behaviour in these environments. The aim of this study was to investigate the feasibility of improving speed perception in a driving simulator by manipulating the Geometric Field Of View (GFOV) of the virtual scene within the projected Field Of View (FOV) of the participant. 16 experienced drivers were asked to produce four target speeds (20, 30, 50, and 70mph) with the speedometer covered. Each target speed was produced under four GFOV/FOV ratios (.83:1, 1:1, 1.17:1, 1.33:1) twice whereby a GFOV/FOV ratio of 1:1 refers to the standard simulator configuration displaying geometrically correct optic flow. Results showed that in the standard configuration, visual speed was consistently underestimated resulting in speed overproduction of 10% on average. The smaller GFOV/FOV ratio of .83:1 led to even greater overproduction, whereas the larger GFOV/FOV ratios reduced the error in speed production. Based on a linear regression, the optimum GFOV/FOV ratio was determined at 1.22:1. It was concluded that manipulation of the GFOV provides a subtle technique to improve the perception and production of speed within simulated and virtual environments.