The UN IWG for Children Left in Vehicles is in Phase 2 developing a new UN Regulation for vehicle categories M₂ and M₃. The draft UN Regulation includes requirements for visual and audible external warnings in buses and coaches to prevent children being left inside. The external warning shall be visual and audible, with the visual warning remaining on for at least 15 seconds then off for no greater than 30 seconds, repeating in cycles lasting no less than 10 minutes, using type approved direction indicator lamps all flashing with the same frequency. The audible warning shall remain on for at least 15 seconds then off for no greater than 30 seconds, repeating in cycles lasting no less than 10 minutes, and shall be greater than 60dB(A). Both warnings shall stop immediately after the physical inspection system is disarmed or the vehicle master control switch is turned on. The IWG intends to permit audible devices approved to UN Regulation No. 28 or UN Regulation No. 165 to generate the external audible warning.