1. Background of cut-off position tolerances for motorcycle headlamp
SLR-28-18/Rev.1
Background of cut-off position tolerances for motorcycle headlamp
IMMA
27/02/2019

2. 1. RID text (ECE/TRANS/WP.29/2018/158)
Current RID text has following requirement about cut-off position tolerances for motorcycle headlamp.(Symmetrical passing beam)
Where a headlamp so aimed does not meet the requirements set out in paragraphs and 5.1., its alignment may be changed, except for headlamps that have no mechanism to adjust horizontal aim, on condition that the axis of the beam is not displaced laterally by more than 0.5 degree to the right or left and vertically by not more than 0.25 degree up or down. To facilitate alignment by means of the "cut-off", the headlamp may be partially occulted in order to sharpen the "cut-off". However, the "cut- off" should not extend beyond the line H-H.
Compare with asymmetrical passing beam and AFS, cut-off position tolerances for type approval test is different not only those angles, but also aiming mechanism as indicated above underlined.

3. 2-1. History of R113 text (Initial provision)
RID comes from R113 text. The first document which defined cut-off position tolerances was as follows.
R S2 (27/02/2004: TRANS-WP29-951) *Newly add Class CS/DS
Where a headlamp so aimed does not meet the requirements set out in paragraphs , and 6.3., its alignment may be changed, except for headlamps that have no mechanism to adjust horizontal aim, on condition that the axis of the beam is not displaced laterally by more than 1 degree (= 44 cm) to the right or left 10/. To facilitate alignment by means of the “cut-off”, the headlamp may be partially occulted in order to sharpen the "cut-off". However, the "cut-off" should not extend beyond the line H-H."
This means that original R113 allowed cut-off position tolerances only for horizontal direction.
That’s why adjustment mechanism of horizontal aim was necessary.

4. 2-2. History of R113 text (Current requirement)
R was effective from 26/07/2012. In that time, requirement of cut- off position tolerances was changed from horizontal only to current text(UP- Down, L-R) to align with the requirement of R112.
The description of horizontal aim should be deleted at the time when it was originally allowed to adjust in the vertical direction.
However, the description is still exist
even though the requirement is updated.

5. 3. Conclusion
Based on this situation, description of horizontal aim is meaningless in current RID text.
From the technology neutral point of view, new Annex in SLR should be removed.