1. COP statistic proposal for UN-WLTP
December 2018

2. COP Objective Evaluation of current procedure acc. 2017/1151
Potential Alternatives

3. Objective
Focus here is on regulated pollutants and CO2 measured in the WLTP test.
The Conformity of Production Process shall verify that the performance of new production vehicles conform with the approved type.
However, due to variation of emission performance from vehicle to vehicle (HW tolerances, variation in test execution, measurement equipment tolerances etc), conformity has to be demonstrated on a suitable statistical basis.
The COP procedure shall not result in any consequential inflation of declared CO2 values compared to measured values in order to demonstrate production compliance.

4. Objective The statistical procedure shall:
Address the low confidence of the standard deviation calculated from the initial sample size (converging pass/fail thresholds)
Balance converging thresholds with the aim of a fast but reliable decision
Maintain a level of parity between COP and in-service conformity procedure for pollutant emissions to avoid one procedure dominating

5. Current cop procedure acc. 2017/1151
The current statistical procedure does not meet the objectives.
Main concern is the extremely small uncertainty area between pass/fail thresholds.
Decision forced in most cases at minimum sample size of 3 vehicles without considering low confidence of the variance.
Low chance to continue testing and demonstrate performance of the batch on a broader basis.
Unknown producer/
environmental risk.

6. Example (CO2) for current cop procedure
ECE R83
Three tests reach a fail decision whereby four would have given a pass decision if a fourth test had been allowed and the series slowly comes to an average below the declaration.
2017/1151

7. Potential alternatives
There are 2 potential alternatives to replace the current statistical procedure:
A1 (“by variables”):
Concept as described in ECE R83, i.e. based on average and standard deviation.
Sample plan shortened from 32 to 16 vehicles
Producer risk adapted to actual in-service conformity (ISC) sample plan.
A2 (“by attributes”):
COP testing following the same sample plan as defined for ISC, i.e. testing by attributes.
With that, producer risk adaption fulfilled.
Definition of COP specific elements substituting outliers.
This includes the option to finally define pollutant & CO2 specific rules.

8. Alternative A1 Concept and calculation method carry over ECE R83.
Pass/fail thresholds re-calculated to approximate the producer risk defined by current ISC statistics. Consumer risk unchanged to ECE R83.
Result: pass/fail thresholds narrowed, keeping a wide uncertainty zone at begin of sampling process.

9. Alternative A2
Sample plan c/o ISC acc. 2017/1151 (pass/fail) with “specific” COP threshold to identify exceedance (substitute of outliers) on single vehicle (to be optimized).

10. Evaluation & Outlook
Status of the proposals is preliminary. Further optimization and validation is needed before solid Evaluation incl. pro/con assessment possible.
Outlook:
Optimization & validation: January + February 2019
Final proposal: Begin of march 2019

11. Back-up

12. Simulations for 2017/1151
Case 1: three vehicles with same value  UZ =NULL
Case 2: sample with high variance  UZ remain very small
Statistic Model in Reg. 1151/2017 NON CONSISTENT AT ALL
Source:CNH Industrial

13. Passing probability = f (sample size)