35. The expert from Spain, Chair of the informal working group on safer transport of children in buses and coaches informed GRSP about the progress (GRSP-71-03). She confirmed that the group was developing a first phase assessing: (a) buses and coaches M2 and M3 categories, excluding those which have areas for standing passengers if they can host ECRS (i.e. Class I and A) and (b) built-in systems. Phase 2, she added, would assess ECRS in combination with the 2-point belt and other classes of buses. At the request of the Chair, GRSP agreed to seek endorsement of WP.29 at its June 2022 session to extend the IWG mandate until March 2024.