This Technical Specification describes a test method for measuring a quantity representative of the intrinsic characteristics of sound reflection from railway noise barriers: the reflection index. The test method is intended for the following applications: - determination of the intrinsic characteristics of sound reflection of noise barriers to be installed along railways, to be measured either on typical installations alongside railways or on a relevant sample section; - determination of the in situ intrinsic characteristics of sound reflection of noise barriers and claddings in actual use; - comparison of design specifications with actual performance data after the completion of the construction work; - verification of the long term performance of noise barriers and claddings (with a repeated application of the method). The test method is not intended for the following applications: - determination of the intrinsic characteristics of sound reflection of noise reducing devices to be installed in reverberant conditions, e.g. inside tunnels or deep trenches. Results are expressed as a function of frequency, in one-third octave bands between 100 Hz and 5 kHz. If it is not possible to get valid measurements results over the whole frequency range indicated, the results should be given in a restricted frequency range and the reasons of the restriction(s) should be clearly reported. All noise reducing devices different from noise barriers and related devices acting on airborne sound propagation, e.g. devices for attenuation of ground borne vibration and on board devices are out of the scope of this Technical Specification.