24. Recalling the purpose of ECE/TRANS/WP.29/2013/66, the Chair of GRRF stressed that WP.29 was expecting GRRF to conclude its deliberation about the wet grip limit values. The GRRF experts introduced their positions (GRRF-76-05, GRRF-76-07, GRRF-76-08, GRRF-76-11, GRRF-76-12, GRRF-76-26, GRRF-76-27, GRRF-76-28). The expert from the EC reported on the concerns expressed by the Directorate-General for Mobility and Transport of the European Commission (DG Move). GRRF confirmed the limit values proposed in para. 6.2.2. for Tyres of C2 category and agreed to amend the proposed limit values in para. 6.2.3. for Tyres of C3 category in ECE/TRANS/WP.29/2013/66. GRRF requested the secretariat to submit this amendment as reproduced in WP.29-162-05 to WP.29 and AC.1 for consideration at their March 2014 session.

24bis. The expert from the Russian Federation presented GRB-59-02 proposing a tyre rolling resistance test results evaluation using a mathematical algorithm, to be added as an alternative to the existing one in the text of the Regulation. He also presented the results of a validation study of the proposed algorithm for tyres of the C1 category performed in France, in cooperation with the Russian Federation (GRB-59-07 and GRB-59-08). GRRF noted that this proposal may be submitted by GRB to WP.29 as a supplement to UN Regulation No. 117. GRRF recommended further steps for a better understanding of the proposed method’s sensitivity, suggesting: (i) extending the validation study for tyres of categories C2 and C3 and (ii) verifying the application of the proposed alternative in the conditions of the conformity of production. The GRRF Chair invited the experts to provide their comments on the proposal to the GRB secretariat with a copy to the expert from the Russian Federation.

17. The experts from France, the Russian Federation and ERTRO informed GRB (GRB-59-07 and GRB-59-08) about the outcome of their ad hoc meeting on testing the “Deceleration Calculator” software proposed by the Russian Federation for the deceleration test method using the dω/dt form for measuring rolling resistance. GRB noted that the ad hoc meeting had been hosted by the Technical Union for the Automobile, Motorcycle and Cycle Industries (UTAC), and generally included both theoretical justification of the method and its experimental assessment by determining rolling resistance of a sample tyre of class C1 using two test machines of different types. GRB also noted that the obtained data, its processing and statistical assessment had demonstrated good adaptability of the software to the tyre test machines and satisfactory reproducibility of deceleration data. Moreover, the algorithm of the “Deceleration Calculator” practically provides independence of the measured deceleration from the test speed range in span from 4 to 20 km/h.

18. Therefore the expert from the Russian Federation proposed GRB-59-02 superseding ECE/TRANS/WP.29/GRB/2013/10, as an alternative for measurements and data processing for deceleration value obtaining in differential form dω/dt.

19. GRB agreed in principle with the proposed method. However, given the late availability of GRB-59-02, GRB suggested that this document, accompanied by other supporting materials (GRB-59-07 and GRB-59-08), be first submitted to the forthcoming February 2014 session of GRRF for discussion and then, together with GRRF comments, transmitted as an official document to the next GRB session in September 2014 for final consideration. In the meantime, it was noted that results of testing tyres of commercial vehicles (classes C2 and C3) could also become available for that session of GRB. Finally, GRB invited experts to provide comments, if any, to the secretariat before the next GRB session.