This handbook is the second deliverable of SaPPART COST Action, dedicated to performance issues, when positioning performance is essential to the fulfilment of the requirements of the whole ITS system. It starts by illustrating the non-straightforward nature of the role of positioning information in some emblematic applications and introduces a simulation method sensitivity analysis, as a tool to make the right choice of positioning terminal for a given application. Then, the Handbook discusses the error sources at the terminal level and introduces a model of the horizontal position error in an urban environment. In the final part, this error model and the sensitivity analysis are applied to two examples of ITS systems, namely Road User Charging and eCall, in order to illustrate how sensitive these systems are to the positioning performance.