Due to the seamless guidance by rails, the railway system requires a dedicated signalling sub-system, whereby a major part of the functionality must be ensured and controlled on the infrastructure side. From a European perspective, the traditional signalling is one of the most conservative parts of the railway system strongly bound to the national traditions by all involved parties. Since 1990 the EU is promoting the reformation of parts of the signalling subsystem under the ERTMS programme.

However this covers not the whole signalling system. The implementation of ETCS could be hampered, in areas of the conventional European rail network, where interlocking will need to be replaced, if this cannot be carried out in an economically and technically efficient manner. Also the implementation of systems utilising centralised and automated route-setting of trains will be economically constrained. Railways are aiming for significantly reduced life-cycle costs of future interlocking and associated outdoor equipment. Standardisation, increased competitive tendering and significant reduction of implementation time are considered to be key requirements for the future. Without an approach, similar to that underway for ERTMS-ETCS, many suppliers will run into resource constraints, making it difficult for them to keep up with the many new concurrent developments.

Therefore, railways and the signalling supply industry agree that the scope of INESS should be the interlocking up to the point of interfaces with the surrounding other signalling and train control systems like centralised traffic control, neighbouring interlocking, ETCS Radio-block centres and possibly object controllers for out-door devices. INESS will adopt the CENELEC norm with the underlying system engineering principles. It will build on the available results of both the Euro-Interlocking project and the ERTMS developments and it will especially not modify the current ETCS functionalities and solutions.