Document ID: chunk:federal_register_of_legislation:F2015C00542:reg:254:p14
Version: federal_register_of_legislation:F2015C00542
Segment Type: reg
Provision Reference: reg 254 (pt 14/18)
Character Range: 136439–139366

a checking template

               When a rapid assessment with a possible margin of error of up to 20 per cent is sufficient, calculate the value of A (see Figure 10) from the limit value L for the change in deviation and the value of R2, the distance from the safety glazing to the display screen:
               A = 0.145 L - R2
               The relationship between the change in diameter of the projected image d and the change in angular deviation  is given by
               d = 0.29   R2
               where:
               d is in millimetres,
               A is in millimetres,
               L is in minutes of arc,
                is in minutes of arc,
               R2 is in metres.

              9.2.1.3.3. Measurement using a photoelectric device

               Where a precise measurement with a possible margin of error of less than 10 per cent of the limit value is required, measure d on the projection axis, the value of the spot width being taken at the point where the luminance is 0.5 times the maximum spot-luminance value.
              9.2.1.4. Expression of results

               Evaluate the optical distortion of the windscreen by measuring d at any point of the surface and in all directions in order to find d max.
              9.2.1.5. Alternative method

               In addition, a strioscopic technique is permitted as an alternative to the projection techniques, provided that the accuracy of the measurements given in paragraphs 9.2.1.3.2. and 9.2.1.3.3. is maintained.

              9.2.1.6. The distance  x shall be 4 mm.

              9.2.1.7. The windscreen shall be mounted at the same angle of inclination as on the vehicle.

              9.2.1.8. The projection axis in the horizontal plane shall be maintained approximately normal to the trace of the windscreen in that plane.

              9.2.2. The measurements shall be performed:

              9.2.2.1. For vehicle category M1 in test area A, extended to the median plane of the vehicle, and in the corresponding part of the windscreen symmetrical to it about the longitudinal median plane of the vehicle, and also in the reduced test area B according to paragraph 2.4. of Annex 18.

              9.2.2.2. For vehicles of categories M and N other than M1:

                  (a) In zone I as defined in paragraph 9.2.5.2. of this annex for M2, M3, N2 and N3 vehicles;

                  (b) Either in zone I as defined in paragraph 9.2.5.2. of this annex or in test area A, extended to the median plane of the vehicle, and in the corresponding part of the windscreen symmetrical to it about the longitudinal median plane of the vehicle, and also in the reduced test area B according to paragraph 2.4. of Annex 18 for N1 vehicles.

              9.2.2.3. For agricultural and forestry tractors and for construction-site vehicles for which it is not possible to determine zone I, in zone I'