Integrity: A Key Enabler for Liability Critical Applications

"In the field of GNSS (Global Navigation Satellite System), integrity is an essential navigation performance for different applications. New initiatives are being developed in the USA, Europe and other regions to ensure the integrity of the GNSS signals either through specific augmentations to existing systems (as is the case of WAAS and EGNOS) or as a built-in feature (as is the case of the future GPS-III and Galileo). While integrity is mainly conceived for Safety of Life critical applications and, in particular, for civil aviation (whose requirements today drive the development of integrity related systems), it is strongly believed that integrity will be the booster for a new set of applications that will constitute a new breakthrough in GNSS. Integrity is not only highly valuable for Safety of Life applications but also more generally for what the authors call Liability Critical applications. These are applications where undetected GNSS mis-performances can generate significant legal or economic consequences such some types of law enforcement, road charging and automatic tolling applications. Thus, integrity will be an essential enabler for those applications either directly affecting the economic results of a business or having any legal impact. The road sector provides one of the best examples for those two types of applications, in particular in road charging and traffic law enforcement. The current trend within worldwide road infrastructure public authorities is to encourage road charging mechanisms that, without restricting mobility, distribute infrastructure capital and operational costs among users more evenly. Moreover, congestion problems in metropolitan areas are making public authorities consider congestion control mechanisms. Road charging systems based on GNSS, provide significant advantages in implementing these policies especially because of flexibility and cost efficiency. However, because of the direct impact on charging, it is essential to guarantee the integrity of the computed position in order to avoid erroneous charging that would make the application unfeasible. In addition, social and political claims exist to improve the safety of the roads and a key way to do this is to apply more severe traffic law enforcement. This, in practice, implies a more systematic monitoring of driver behavior and respect for traffic rules. GNSS also provides a powerful technology for this purpose but, again, a guarantee is needed to ensure that only real infractions (and not GNSS errors) are penalized. Otherwise, unexpected positioning/velocity errors might result in the mis-application of penalties. These ideas are generalized in the mentioned Liability Critical applications, i.e. those applications having liabilities either from the economic or legal viewpoints and for which the integrity is linked to a legal truth (compare this with safety critical applications where integrity is linked to a personOs safety). This paper analyzes the above mentioned Liability Critical applications paying special attention to the road sector ones. It will further investigate the major challenges for its implementation with special attention devoted to the technological aspects."