Connected to the French N20, it connects Puigcerdà to Barcelona, its total distance is of 165 km in lining of C-16 E09 passing by the Tunnel of Cadi and Manresa.

Its layout is very sinuous between Puigcerda and Ripoll, also the majority of the motorists in source or going to Barcelona generally prefer to borrow the Tunnel of Cadi which leads to the C-16, thus getting a better comfort.

It fits in the axis Paris - Orleans - Limoges - Toulouse - Barcelona.

Nowadays, it is absorbed by the C-17 between Ripoll and Granollers whose majority of the sections are in 2 X 2 ways.