Today, Intelligent Transportation Systems (ITS) and Personal Mobility (PM) applications are one of the most promising markets for GNSS. However, the high influence of operational and environmental conditions on GNSS performance in the road sector has led to various standardization initiatives that despite their substantial contribution many scientific issues are still open and a unified certification process is missing. SaPPART (Satellite Positioning Performance Assessment for Road Transport, TU1302) is a COST Action the aim of which is to develop a common framework for the definition, assessment and certification of GNSS service levels for ITS and PM applications through a pan-European research oriented network that brings together scientists from the Geodesy, Geomatic Engineering and Transportation sectors. The scope of this presentation is twofold. Firstly, to introduce the SaPPART Action, its objectives, range of activities and achievements as a whole. Secondly, to discuss the main issues and challenges related to GNSS positioning accuracy and integrity in the road environment and in relation to challenging road applications. In this line, it reviews summary results and perspectives from a selection of Short Term Scientific Missions (STSM) undertaken between participating research teams in the SaPPART COST Action. Particularly, it outlines the findings from a number of independent experimental testing and simulation studies that aim at generating and assessing vehicle trajectories based on their position, velocity, time (PVT) error estimates and models respectively and in relation to a reference trajectory.