i) reviewing the classification of national roads systems and the definition of the RTRN. ARTICLE 4.5 FUNDING SOURCES 1. Member States agree to develop and implement cohesive and definitive road funding policies with a view to a) identifying adequate, sustainable and appropriate sources of road funding which includes general revenue, road user charges and funds generated jointly by the public and private sectors; b) increasing transparency in the road funding process; c) ensuring that revenues obtained from road users under road user charges shall be regarded as dedicated for the provision, maintenance and operation of roads; d) ensuring that road users, including foreign road users, contribute to the full costs of maintaining roads and progressively contribute to the full costs of providing roads while (i) ensuring that the revenues obtained from foreign road users are devoted to the maintenance of the RTRN within their respective territories; (ii) ensuring that the use of roads is priced so as to improve economic efficiency in road transport; and (iii) promoting equity between different categories of road users; e) ensuring that Member States shall apply the principle of non-discrimination in implementing road user charging instruments to foreign road users. 2. In order to promote harmonised national road user charging systems, Members States shall develop a common understanding in respect of the types of road user charging and the levels of such charges and introduce in their respective territories on the basis of regular exchange of information a) fuel levies (designated as road charges); b) vehicle licence fees; c) road tolls; d) abnormal and awkward load charges; e) weight-distance type charges; f) cross-border road user charges; g) entry fees payable by foreign registered vehicles; and (h) parking and traffic congestion costs.