This document specifies product characteristics for road traffic noise reducing devices (RTNRD) - as defined in 3.1 - to be used alongside roads to reduce the propagation of traffic noise away from the road environment. The following types of road traffic noise reducing devices are covered by this document:- noise barriers (as defined in 3.4);- claddings (as defined in 3.5);- covers (as defined in 3.6); and- added devices (as defined in 3.7).Road traffic noise reducing devices comprise acoustic elements (as defined in 3.2), structural elements (as defined in 3.3) or self-supporting elements (having both acoustic and structural functions).This document identifies assessment and verification of constancy of performance (AVCP) of characteristics of road traffic noise reducing devices.This document does not cover the following: - resistance of RTNRD to vandalism, - visual appearance of RTNRD, and acoustic properties of road pavements.