Proposal to further refine the transitional provisions of UN R48. In 2014, the transitional provisions of UN R48 were changed in order to avoid having more than one series of amendments in force at the same time (via Supplement 3 to the 06 series of amendments). This change allows earlier series of amendments to be “frozen” and used under the International Whole Vehicle Type Approval system (IWVTA) as “versions” of UN R48. However, the possibility for the partial application of a series of amendments resulting from the installation of new equipment on a vehicle approved to an earlier series has been raised within the IWVTA. This proposal refines the transitional provisions in order to enable partial application of a series through an extension of the existing approval rather by requiring a new approval. At the same time, the proposal aims to ensure that the safety objectives of UN R48 are met.