This tutorial paper highlights possible issues related to the integrity and authentication of the GNSS position in road applications. In fact, the Global Navigation Satellite System (GNSS) community is already aware of the conceptual and practical problems related to the availability of the position integrity (i.e. position confidence, protection level) and authentication in urban scenarios. However, these issues seem not to be widely known in the Intelligent Transportation Systems (ITS) domain. These limitations need to be carefully considered and addressed in the perspective of deploying reliable and robust systems based on positioning information.