Document ID: chunk:federal_register_of_legislation:F2015C00542:reg:254:p16
Version: federal_register_of_legislation:F2015C00542
Segment Type: reg
Provision Reference: reg 254 (pt 16/18)
Character Range: 141909–145130

zone I, zone I' consists in the whole surface of the windscreen.

              9.2.6. Interpretation of results

              A windscreen type shall be considered satisfactory with respect to optical distortion if, in the four windscreens submitted for testing, optical distortion does not exceed the values given below for each zone or test area.

Vehicle category                                                             Zone                                      Maximum values of optical distortion
M1 and N1                                                                    A - extended according to para. 9.2.2.1.  2' of arc

B - reduced according to para. 2.4. of Annex 18                              6' of arc
M and N categories other than M1                                             I                                         2' of arc
Agricultural vehicles etc. for which it is not possible to determine zone I  I'                                        2' of arc

9.2.6.1. No measurements shall be made in a peripheral area 25 mm inboard of the design glass outline and of any opaque obscuration, provided that it does not impinge into the extended zone A or zone I.
              9.2.6.2. For agricultural and forestry tractors and for construction-site vehicles, no measurements shall be made in a peripheral area 100 mm wide.

              9.2.6.3. In the case of split windscreens, no measurements shall be made in a strip 35 mm from the edge of the windscreen, which is adjacent to the dividing, pillar.

              9.2.6.4. A maximum value of 6' of arc is permitted for all portions of zone I or zone A in a peripheral area 100 mm inboard of the design glass outline.

              9.2.6.5. Slight deviations from the requirements may be allowed in the reduced test area B according to paragraph 2.4. of Annex 18 provided they are localized and recorded in the report.

              9.3. Secondary-image-separation test

              9.3.1. Scope

               Two test methods are recognized:

               Target test, and

               Collimation-telescope test.

               These test methods may be used for approval, quality-control or product-evaluation purposes, as appropriate.

              9.3.1.1. Target test

              9.3.1.1.1. Apparatus

               This method involves viewing an illuminated target through the safety glazing. The target may be designed in such a way that the test can be carried out on a simple 'go-no go' basis.

               The target shall preferably be of one of the following types; that is to say, either

                  (a) An illuminated 'ring' target whose outer diameter, D, subtends an angle of n minutes of arc at a point situated at x metres (Figure 11(a)), or

                  (b) An illuminated 'ring and spot' target whose dimensions are such that the distance D from a point on the edge of the spot to the nearest point on the inside of the circle subtends an angle of n minutes of arc at a point situated at x metres (Figure 11(b)), where

                 n is the limit value of secondary-image separation,

                    x is the distance from the safety glazing to the target (not less than 7 m),