Document ID: chunk:federal_register_of_legislation:F2015C00542:reg:254:p12
Version: federal_register_of_legislation:F2015C00542
Segment Type: reg
Provision Reference: reg 254 (pt 12/18)
Character Range: 130623–133843

thickness characteristics identical to those of the actual windscreen, the measurements being taken normal (perpendicular) to the glass pane.

              9.1.2.2. For the windscreens of M1 vehicles[16]  the test shall be carried out in test area B defined in Annex 18, paragraph 2.3., excluding any opaque obscuration impinging on it.

               For the windscreens of N1 vehicles, the manufacturer may request that the same test may be carried out either in test area B defined in Annex 18, paragraph 2.3., excluding any opaque obscuration impinging on it, or in the zone I defined in paragraph 9.2.5.2.3. of this annex.

               For windscreens of other categories of vehicles, the test shall be carried out in the zone I defined in paragraph 9.2.5.2.3. of this annex.

               However, for agricultural and forestry tractors and for construction-site vehicles for which it is not possible to determine zone I, the test shall be carried out in zone I' as defined in paragraph 9.2.5.3. of this annex.

              9.1.3. Indices of difficulty of the secondary characteristics

                                        Colourless    Tinted

Colouring of the glass                  1             2
Colouring of the interlayer             1             2
(in the case of laminated windscreens)

                                        Not included  Included

Shade and/or opaque obscuration         1             2

               The other secondary characteristics are not involved.

              9.1.4. Interpretation of results

               The regular light transmittance shall be measured according to paragraph 9.1.2. of this annex and the result shall be recorded. In the case of a windscreen, it shall not be less than 70 per cent. In the case of glazing other than a windscreen, the requirements are specified in Annex 21.

              9.2. Optical distortion test

              9.2.1. Scope

               The method specified is a projection method which permits evaluation of the optical distortion of a safety glazing.

              9.2.1.1. Definitions

              9.2.1.1.1. "Optical deviation" means the angle between the true and the apparent direction of a point viewed through the windscreen, the magnitude of the angle being a function of the angle of incidence of the line of sight, the thickness and inclination of the windscreen, and the radius of curvature "r" at the point of incidence.

              9.2.1.1.2. Optical distortion in a direction M-M': The algebraic difference in angular deviation  measured between two points M and M' on the surface of the glass pane, the distance between the two points being such that their projections in a plane at right angles to the direction of vision are separated by a given distance x (see Figure 6).

               Anti-clockwise deviation should be regarded as positive and clockwise deviation as negative.

              9.2.1.1.3. Optical distortion at a point M: The optical-distortion maximum for all directions M-M' from the point M.

Figure 6

Diagrammatic representation of optical distortion

       Notes:

                        = 1 - 2,  i.e. the optical distortion in the direction M-M'.