In this master’s thesis we set out to explore how input and output of in-vehicle systems affect driving performance. Our contribution to the field of in-vehicle systems constitutes two research papers. In the first research paper we assessed various configurations of an in-vehicle system with an equal emphasis on input and output modalities – through this assessment we sought to explore how these modalities separately affect driving performance. Based on the first paper we decided to explore output modalities further. We evaluated how different output modalities affect driving performance by comparing three output configurations of a GPS system; audio, visual and audio-visual combined. We conducted a field experiment in real traffic; we hereby sought to elicit insight into user behaviour within an approximated natural context.