45. GRSG resumed discussion on the proposal of CLCCR on assisting driven axles of trailers (ECE/TRANS/WP.29/GRSG/2023/5). The expert from Germany mentioned GRSG-127-01 and explained that the investigation of the Federal Highway Research Institute (BASt) of Germany had been presented at the October 2023 session of GRSG. He added that the current definition of trailers need not be changed if the trailers lacked a driving force. The expert from the Netherlands reminded GRSG that the issue should be dealt with differently in working groups. He announced that a revised proposal was prepared by CLCCR, France and the Netherlands for the upcoming GRSP that addresses UN Regulation No. 100 (Electric power trained vehicles). He clarified that the proposal would also consider the trailer as a generator of electricity in a first stage and possible traction to compensate for internal losses in a second stage. The OICA expert endorsed the statement from the expert from the Netherlands and informed GRSG that a proposal addressing this kind of trailer was under discussion in GRVA. The expert from China informed GRSG that in his country, studies had been developed and research made on this subject. GRSG agreed to resume discussion on this subject at its October 2024 session.

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.

56. The expert from CLCCR introduced ECE/TRANS/WP.29/GRSG/2022/17 to amend the consolidated Resolution on the Construction of Vehicles (R.E.3) by clarifying 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 United Kingdom remarked on an inconsistency in the text of the proposal between the contribution to the propelling forces of the vehicle combination at all speeds and the speed limit of 15 km/h. The expert from the Netherlands added that amending R.E.3. and Special Resolution No. 1 (S.R.1) would be just a first step because a number of UN Regulations also need amendment (e.g. UN Regulations Nos. 13, 55 and 100) to allow for the introduction of such semi-trailers and full-trailers.

57. Finally, GRSG agreed to resume discussion on this subject at its October 2022 session on the basis of a revised proposal superseding ECE/TRANS/WP.29/GRSG/2022/17.

115. The expert from CLCCR held a presentation on Advanced axles in trailers, addressing new technologies to reduce CO2 emissions for vehicle combinations, with the aim of launching discussions within GRSG on the subject matter. The presentation contained information on the state of the art of the development of independently driven trailer axels using a dedicated electric power source, highlighting that electric trailer propulsion offers a wide range of applications (recuperation, acceleration, support start/stop manoeuvres) which could contribute to lowering CO2 emissions of vehicles. He explained that the introduction of such technology in the market would require the amendment of the definition of trailers in R.E.3 and in the Special Resolution No. 1 concerning the common definitions of vehicle categories, masses, and dimensions (S.R.1), as well as its alignment in several relevant UN Regulations (Nos. 13 and 100). He asked GRSG experts for feedback concerning the potential amendment of the relevant definitions, inquired concerning interest in possible discussions on the subject matter among interested stakeholders, and proposed that CLCCR put forth a proposal in this respect at the October 2021 session of GRSG.

116. Following comments and feedback from France, Germany, the Netherlands and the European Commission, addressing potential safety implications that the new technology poises in terms of the interaction of the trailed and the towing vehicle, GRSG invited interested stakeholders to work with CLCCR on this topic towards potentially tabling a proposal that would allow the emerging technology to be aligned with UN Regulations at the upcoming sessions of GRSG.