13. The expert from CLEPA introduced GRB-55-11 concerning the results of a test performed by his organization on additional sound emission provisions (ASEP) of exhaust replacement systems. Moreover, he gave a further presentation (GRB-55-17) showing that as an outcome of the test, two possible alternatives were possible to settle ASEP within UN Regulation No. 59: (i) test should only apply for replacement systems with the same acceptance criteria as for original equipment by using test method A or B or (ii) test should be carried out back to back to original equipment and replacement system. Most of GRB experts stated that it was too premature to indicate the most appropriate alternative. GRB agreed to resume discussion on this subject on the basis of a concrete proposal prepared by the experts from the Netherlands and CLEPA.