Under the umbrella of ITS can be found things as diverse as eCall, which generates an automatic call to an emergency call centre in the case of an accident, road toll systems, which are systems designed to collect road charges, and the already widely known GPS systems, which many of us have in our cars to help us navigate through unknown terrain.

The required accuracy of the location information and the needed coverage implies the use of Global Navigation Satellite Service (GNSS), using GPS and in the near future the European Satellite Navigation Systems Galileo[14] which will offer even greater accuracy and availability.

The required accuracy of the location information and the needed coverage implicate the use of Global Navigation Satellite Service (GNSS), using GPS and in the near future the European Satellite Navigation Systems Galileo[21] which will offer even greater accuracy and availability.

A report commissioned by the American authorities [4] highlights the vulnerability of the entire US transport infrastructure, which is increasingly dependent on the American satellite radionavigation system, GPS, used both as an aid to navigation and as a tool to determine the precise position of vehicles within new improved surveillance systems and as a synchronisation reference for the majority of networks (energy, telecommunications, etc.). It concludes: "The civil transportation sector, seeking the increased efficiency made possible by GPS, is developing a reliance on GPS ...[+++] that can lead to serious consequences if the service is disrupted, and the applications are not prepared with mitigating equipment and operational procedures".

EGNOS (European Geostationary Navigation Overlay System), which monitors the performance of the existing GPS and Glonass systems and reports to users on their performance, continued to receive TEN-T support in its critical design phase, while the ESTB (EGNOS System Test Bed) has been providing a real EGNOS space signal since February 2000.

Building on experience gained within EGNOS [11] for the development of an augmentation system for GPS and GLONASS, Europe has recognised the importance of having a global navigation satellite system conceived as a civil system, and has launched the definition phase of GALILEO.