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‘Field of vision’ means all forward and lateral directions in which the driver of the tractor can see.
‘Reference point’ means the position, fixed by convention, of the tractor driver's eyes notionally located at a single point. The reference point is situated in the plane parallel to the longitudinal median plane of the tractor and passing through the centre of the seat, 700 mm vertically above the line of intersection of that plane and the surface of the seat and 270 mm in the direction of the pelvic support from the vertical plane passing through the front edge of the surface of the seat and perpendicular to the longitudinal median plane of the tractor (Figure 1). The reference point thus determined relates to the seat when unoccupied and fitted in the central position specified by the tractor manufacturer.
‘Semi-circle of vision’ means the semi-circle described by a radius of 12 m about a point situated in the horizontal plane of the road vertically below the reference point, in such a way that, when facing the direction of motion, the arc of the semi-circle lies in front of the tractor, while the diameter bounding the semi-circle is at right angles to the longitudinal axis of the tractor (Figure 2).
‘Masking effect’ means the chords of the sectors of the semi-circle of vision which cannot be seen owing to structural components such as roof-pillars, air intakes or exhaust stacks and the frame of the windscreen.
‘Sector of vision’ means that part of the field of vision bounded:
at the top,
by a horizontal plane passing through the reference point;
in the plane of the road,
by the zone lying outside the semi-circle of vision, and forming the continuation of the sector of the semi-circle of vision, the chord of which is 9,5 m long, perpendicular to the plane parallel to the longitudinal median plane of the tractor passing through the centre of the driver's seat and bisected by that plane.
‘Swept area of the windscreen wipers’ means the area of the outer surface of the windscreen swept by the windscreen wipers.
The tractor shall be constructed and equipped in such a way that, in road traffic and in farm and forest use, the driver has an adequate field of vision, under all the usual conditions pertaining to highway use and to work undertaken in fields and forests. The field of vision is considered adequate when the driver has, as far as possible, a view of part of each front wheel and when the following requirements are fulfilled.
The silhouette (deepest shadow) overlaps projected on to the semi-circle of vision by the masking component when the light sources are switched on simultaneously or alternately must be measured in accordance with point 1.4 (Figure 3).
in which:
is the distance in millimetres between the component obstructing vision and the reference point measured along the visual radius joining the reference point, the centre of the component and the perimeter of the semi-circle of vision; and
is the width in millimetres of the component obstructing vision measured horizontally and perpendicular to the visual radius.
For the purpose of determining the masking effects in the sector of vision, the masking effects due to the frame of the windscreen and to any other obstacle may, in accordance with the provisions of point 2.2.1.4, be considered as a single effect, provided that the distance between the outermost points of this masking effect does not exceed 700 mm.