Research Papers

Visual Scale Factor for Speed Perception

[+] Author and Article Information
Florent Colombet, Damien Paillot, Frédéric Mérienne

 Arts et Métiers ParisTech, Le2i, CNRS, Institut Image, Rue Thomas Dumorey, 71100 Chalon sur Saône, Franceflorent.colombet@gmail.com

Andras Kemeny

RENAULT, Technical Centre for Simulation, Avenue du Golf, 78288 Guyancourt, France; Arts et Métiers ParisTech Le2i, CNRS,  Institut Image, Rue Thomas Dumorey, 71100 Chalon sur Saône, Franceandras.kemeny@renault.com

J. Comput. Inf. Sci. Eng 11(4), 041010 (Dec 06, 2011) (6 pages) doi:10.1115/1.4005449 History: Received October 11, 2011; Revised November 07, 2011; Published December 06, 2011; Online December 06, 2011

Speed perception is an important task depending mainly on optic flow that the driver must perform continuously to control his/her vehicle. Unfortunately, it appears that in some driving simulators speed perception is under estimated, leading into speed production higher than in real conditions. Perceptual validity is then not good enough to study driver’s behavior. To solve this problem, a technique has recently seen the light, which consists of modifying the geometric field of view (GFOV) while keeping the real field of view (FOV) constant. We define our visual scale factor as the ratio between the GFOV and the FOV. The present study has been carried out on the SAAM dynamic driving simulator and aims at determining the precise effect of this visual scale factor on the speed perception. Twenty subjects have reproduced two speeds (50 and 90 km/h) without knowing the numerical values of these consigns, with five different visual scale factors: 0.70, 0.85, 1.00, 1.15, and 1.30. We show that speed perception significantly increases when the visual factor increases. A 0.15 modification of this factor is enough to obtain a significant effect. Furthermore, the relative variation of the speed perception is proportional to the visual scale factor. Besides, the modification of the geometric field of view remained unnoticed by all the subjects, which implies that this technique can be easily used to make drivers to reduce their speed in driving simulation conditions. However, this technique may also modify perception of distances.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

Relations between the geometric field of view and the perceived speed

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Figure 2

Images of the same field of speeds computed with different visual scale factors

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Figure 3

SAAM dynamic driving simulator (Arts et Métiers ParisTech/Renault)

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Figure 4

Screenshots taken with visual scale factors of 0.70, 0.85, 1.00, 1.15 and 1.30 in, respectively, (a), (b), (c), (d), and (e). All these screenshots correspond to only the center image displayed in the simulator (corresponding to 52° of driver’s horizontal field of view).

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Figure 5

Reached speed (on the left) and mean reached speed (on the right) as functions of visual scale factor for both speed consigns (50 km/h in blue circles and 90 km/h in red triangles). Vertical error bars represent 95% confidence level.

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Figure 6

The variation of produced speed (and of perceived speed) generated by the visual scale factor is proportional to the speed consign

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Figure 7

Error (on the left) and mean error (on the right) relative to speed consign displayed as functions of visual scale factor. Vertical error bars represent 95% confidence level.

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Figure 8

Error (on the left) and mean error (on the right) relative to speed reached by the same subject with the same speed consign with a visual scale factor of 1.0, as functions of visual scale factor. Vertical error bars represent 95% confidence level.



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