32. The experts from CLCCR and CLEPA introduced GRSG-124-12 superseding ECE/TRANS/WP.29/GRSG/2022/17, to clarify the definition of a trailer/semi-trailer in case one or more trailer axles may be driven by a propulsion type integrated into the trailer (e.g. electric engine) in combination with the motor vehicle. The expert from the Netherlands expressed a study reservation on the proposal and recommended that parallel amendments be introduced in other UN Regulations such as UN Regulation No. 13 (Heavy vehicle braking). At the same time, he recalled to GRSG that UN Regulation No. 100 does not apply to trailer categories O3 and O4. GRSG agreed to resume discussion at its March 2023 session and requested the secretariat to distribute GRSG-124-12 with an official symbol.