In introducing ASEP in Annex 7 in 2016, the scope was limited to vehicles with internal combustion engines (ICE) based on the experience of variabilities in the exhaust silencing systems. Electric driven vehicles have been exempted from ASEP. For electric driven vehicles the new UN Regulation No. 138, dealing with the reduced audibility of these vehicles, was worked out until 2017. At that moment no one expected sound enhancement systems beyond the scope and aim of UN R138.

This proposal is an approach to address the concern that electric vehicles might be equipped with sound enhancement systems beyond the scope and aim of UN R138. This proposal does not require any changes to UN R138.01. This proposal is given as a supplement to enable the quickest entry into force, providing all manufacturers clear direction on the design of sound enhancement systems.