Paper abstract bibtex
Steering down a road can be modelled using two (potentially competing) control mechanisms – the driver needs to anticipate future steering requirements (guidance control) whilst simultaneously stabilising position-in-lane (compensatory control). Influential models of steering have managed to capture many steering behaviours using just 'far' and 'near' road regions to inform guidance and compensatory control respectively (Salvucci & Gray, 2004). However, optic flow can influence steering even when road edges are visible (Kountouriotis et al., 2013; 2015). The present study assessed whether flow selectively interacts with compensatory and/or guidance modes of steering control. In two experiments participants steered through a virtual reality computer-simulated environment. Optic flow speed was manipulated independent of the veridical road edges so that use of flow would lead to predictable understeering or oversteering. Experiment 1 created conditions whereby only Near road, Far road, or Complete road information was available. Gaze was either unconstrained, or constrained to fixate the centre of the road 1.2s ahead. Large Flow-Induced Steering Biases (FISB) were observed in Far and Complete conditions, which is consistent with flow speed selectively interacting with guidance control. Similar patterns of FISB were observed across both gaze conditions, so Experiment 2 constrained gaze, and examined the Flow × Road interaction further using Five flow speeds (.5, .75, 1, 1.25, 1.5; proportional to veridical) and eight combinations of Near, Middle and Far road components. Steering was found to systematically vary according to flow speed, but crucially FISB magnitude depended on which road-edge components were visible. The presence of a guidance signal increased the influence of flow, with the largest FISB in Far and Complete road conditions, and the smallest FISB was when only Near road-edges were visible. Overall these results show that optic flow can act indirectly upon steering control by modulating the guidance signal provided by the Middle and Far road edges.