Research Programme Operations and Management. Research into traffic signs and signals at level crossings Appendix L: Equipment for road user trials

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1 Research Programme Operations and Management Research into traffic signs and signals at level crossings Appendix L: Equipment for road user trials

2 Copyright RAIL SAFETY AND STANDARDS BOARD LTD ALL RIGHTS RESERVED This publication may be reproduced free of charge for research, private study or for internal circulation within an organisation. This is subject to it being reproduced and referenced accurately and not being used in a misleading context. The material must be acknowledged as the copyright of Rail Safety and Standards Board and the title of the publication specified accordingly. For any other use of the material please apply to RSSB's Head of Research and Development for permission. Any additional queries can be directed to enquirydesk@rssb.co.uk. Published: August 2011 Written by:

3 Appendix L - Equipment for road user trials Key items of equipment used during this trial were: TRL's car driving simulator to record visual scenes to be played to participants. A projector and screen to play the visual scenes to participants. A head-mounted eye tracker which was used to identify participants' point of regard. A joystick to allow participants to indicate their preferred speed choice. TRL's car driving simulator uses SCANeR Studio software and this was used to record a series of visual scenes which would be presented to participants. The simulator software allows the driver's point of view to be adjusted and a maximum speed to be set. This would enable, for example, horse riders to view the scenes from the left hand side of the road, and from a point higher than car drivers. Their videos also proceeded at a slower pace than videos for drivers of motorised vehicles. A Christie VividGreen projector was used to project the visual scenes onto a screen. The eye tracker used during this research was the ISCAN VisionTrak ETL-500, supplied by Polhemus. The eye tracker is mounted on a headband that can be adjusted to fit participants' heads. It is fairly light, weighing approximately 170g, although participants were allowed to take breaks and remove the eye tracker between presentations. The VisionTrak system uses a dichroic mirror to reflect the eyeimage onto a highly sensitive head-mounted video camera. The scene camera is mounted below the participant's line-of-sight. The tracking technique used by the system is a 120Hz pupil and corneal dark-eye tracker. As the eye tracker uses dark-eye tracking the image of the eye was not affected by changes in lighting conditions, such as glare or darkness. However, initial testing did find that the scene camera was sensitive to light conditions and did not perform well in a dark room with a bright image projected on a screen. Under such light conditions the scene image suffered from wash-out. As a result it was necessary RSSB 1

4 to adjust the size of the projected image so that it filled much of the participant's visual field. After the eyetracker was fitted, the participant looked at five points in sequence, while the investigator moved a cursor on the video scene screen with the mouse to each point and accepted the point. During the calibration the eye gate was checked to make sure that the pupil and corneal reflection were captured and that the eye was correctly positioned within the camera. The scene was also checked to ensure that the picture captured by the scene camera matched the scene, which the driver observed through the dichroic mirror. The calibration was then conducted and checked. The eye tracker then automatically tracked point of regard and the correlation of the raw eye position to the precise position on the scene. The image focussed on by the participant was identified by crosshairs and instantaneously superimposed on the scene image. The eye tracker headband consisted of a dichroic mirror which was positioned below the eye and was transparent, an infra red illuminator which detected the pupil positions, an eye camera and a camera to film the visual scene. The cameras were ¼'' in diameter. As shown in Figure 21, the scene camera was positioned below the participant's line of sight. Figure 1 - ISCAN VisionTrack eye tracker The participant had complete freedom of movement. The head mounted system allowed the participant full 6 Degrees of Freedom, and the participants' view was not limited in any way. 2 RSSB

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