basic parameters — any regulatory, technical or operational condition which is critical to interoperability and requires a decision in accordance with the procedure laid down in Article 21(2) before any development of draft TSIs by the joint representative body (j)

essential requirements — all the conditions set out in Annex III which must be met by the trans-European conventional rail system, the subsystems, and the interoperability constituents including interfaces (e)

European specification — a common technical specification, a European technical approval or a national standard transposing a European standard, as defined in points 8 to 12 of Article 1 of Directive 93/38/EEC (f)

existing rail system — the structure composed of lines and fixed installations of the existing rail system plus the rolling stock of all categories and origin travelling on that infrastructure (n)

Infrastructure managers — those referred to in Articles 3 and 7 of Directive 91/440/EEC (h)

interoperability — the ability of the trans-European conventional rail system to allow the safe and uninterrupted movement of trains which accomplish the required levels of performance for these lines. This ability rests on all the regulatory, technical and operational conditions which must be met in order to satisfy the essential requirements (b)

interoperability constituents — any elementary component, group of components, subassembly or complete assembly of equipment incorporated or intended to be incorporated into a subsystem upon which the interoperability of the trans-European conventional rail system depends directly or indirectly. The concept of a ‘constituent’ covers both tangible objects and intangible objects such as software (d)

joint representative body — the body bringing together representatives of the infrastructure managers, railway companies and industry which is responsible for drawing up the TSIs (h)

notified bodies — the bodies which are responsible for assessing the conformity or suitability for use of the interoperability constituents or for appraising the ‘EC’ procedure for verification of the subsystems (i)

renewal — any major substitution work on a subsystem or part subsystem which requires fresh authorisation for putting into service within the meaning of Article 14(1) (m)

specific case — any part of the trans-European conventional rail system which needs special provisions in the TSIs, either temporary or definitive, because of geographical, topographical or urban environment constraints or those affecting compatibility with the existing system. This may include in particular railway lines and networks isolated from the rest of the Community, the loading gauge, the track gauge or space between the tracks and rolling stock strictly intended for local, regional or historical use, as well as rolling stock originating from or destined for third countries, as long as this stock does not cross the border between two Member States (k)

subsystems — the result of the division of the trans-European conventional rail system, as shown in Annex II. These subsystems, for which essential requirements must be laid down, are structural and functional (c)

trans-European conventional rail system — the structure, as described in Annex I, composed of lines and fixed installations, of the trans-European transport network, built or upgraded for conventional rail transport and combined rail transport, plus the rolling stock designed to travel on that infrastructure (a)

upgrading — any major modification work on a subsystem or part subsystem which requires fresh authorisation for putting into service within the meaning of Article 14(1) (l)