One of the aims of Directive 2002/49/EC as stated in article 1 is to define a common approach intended to avoid, prevent or reduce the harmful effects due to exposure to environmental noise. Within this framework, the European Commission is working on the assessment of road traffic noise. The noise production of a vehicle is defined by the two main parameters - category, speed - and it also depends on several environmental or specific effects. One of them is the type of road surface, as it can lead to differences in sound levels up to 15 dB for the same traffic flow and composition. Therefore, it becomes of the highest importance to know the influence of the different road surfaces in the vehicle noise emission. At this moment, there is also an open debate within the EU whether to develop some kind of noise classification procedure for the different road surfaces or not. In relation to these subjects, CEDEX is working on the measurement of tyre-road noise with the CPX method in several road surfaces in the Spanish National Road Network. The CPX method, as stated in the ISO/CD11819-2, allows measuring the influence of surface characteristics on tyre-road noise.