C-31 or Eix Costaner is a Catalonia's primary highway. It is the result of merging several sections of previously existing roads, autopistas and autovías after the 2004's renaming of primary highways managed by the Generalitat de Catalunya. According to this new denomination, the first number (C-31) indicates that is a southwest-northeast highway (parallel to the Mediterranean Sea coastline), while the second number (C-31) indicates that is the closest to the Mediterranean Sea.