13. The expert from Germany presented GRRF-80-39 introducing the proposal for an Annex 23 to Regulation No. 13 in ECE/TRANS/WP.29/GRRF/2015/20 with provisions for trailers of category O2 without pneumatic connection and equipped with service braking systems with pneumatic energy storage devices. The proposal received some comments related to possible design restrictions and warning signals. The expert from Germany invited the GRRF experts to a special interested group meeting on the draft Annex 23 of Regulation No. 13 to take place in Bonn (Germany) on 02 November 2015.