According to the 2004's new codification for primary highways managed by the Generalitat de Catalunya, the first number (C-16) indicates that is a south-northbound highway, whereas the second number (C-16) indicates that is the sixth westernmost.
The itinerary starts at Barcelona's Via Augusta and heads northbound crossing the Serra de Collserola's mountain range, through the Vallvidrera's tunnel, and then the comarques of Vallès Occidental, Bages and Berguedà. Most of the path follows the valley of the Llobregat river, hence the name of Eix del Llobregat. Finally it crosses another mountain range, Serra del Cadí, through the Cadí's tunnel, and enters in the comarca of Cerdanya. The path finishes at the connection with road N-260 at Puigcerdà, very close to the french border.
This highway, along with C-17, is a main South-North communication in Catalonia, since it connects Barcelona with several significant inner cities and towns such as Terrassa, Manresa, Berga or Puigcerdà, as well as it is also the straightest and quickest way from Cerdanya comarca and from Andorra to the centre, the South and the East of Catalonia, including its major city and capital, Barcelona.