The former N31 motorway bisected the municipality of Harlingen in two halves. When the authorities decided to increase the capacity of the road they faced the challenge to heal the urban fabric and reunite both halves. The decision was taken to deepen the new motorway over a length of 2 kilometres, thus creating the opportunity to realize this ambition. The new traverse is conceived as an open tunnel and lies at an average depth of 4,6 meters below ground level. Five viaducts and one aqueduct span the traverse. Halfway through the traverse has exits and entrances to the city centre.

N31 Traverse Harlingen | Royal HaskoningDHV

Royal HaskoningDHV is responsible for making the architectural design specifications including the architectural concept of the sand ribble walls, the overpasses, the aqueduct, the rail viaduct and the central traffic junction Harlingen. From 2015 to 2016, Royal HaskoningDHV has been involved in the spatial planning of the ground level area bordering the tunnel traverse.

N31 Traverse Harlingen | Royal HaskoningDHV

The city of Harlingen is depicted by three geographical themes: its vicinity to the Waddenzee, the harbours and the historical centre of the fortress town. We made this ‘couleur locale’ manifest in the design and in the materialization of the traverse and of its viaducts. The inner walls of the traverse and the edges of the viaducts were given a special texture and colour to emphasize and convey the identity of Harlingen.

N31 Traverse Harlingen | Royal HaskoningDHV

N31 Traverse Harlingen | Royal HaskoningDHV

Over a total length of 4 kilometres, the inner tunnel walls are the most eye-catching element of the entire traverse. We chose to bestow the relief and colour of sand ribs to these inner walls, a reference to the ribs of wet sand that cover the beach at low tide, on the brink of land and water.

N31 Traverse Harlingen | Royal HaskoningDHV

N31 Traverse Harlingen | Royal HaskoningDHV

The open tunnel traverse of the N31 has a unambiguous look and feel with a continuous profile. The appearance of all viaducts is generic. In contrast with the inner walls of the traverse, the edges of the viaducts have a pattern of basalt stones that refers to the walls of the local see barrier, a previous design from our team.

N31 Traverse Harlingen | Royal HaskoningDHV

N31 Traverse Harlingen | Royal HaskoningDHV

The entrance to the city from the traverse is an exception to the generic design. Here we chose to extend the basalt pattern, flanked by grass, down into the traverse, as a welcoming gesture to the city.

N31 Traverse Harlingen | Royal HaskoningDHV

N31 Traverse Harlingen | Royal HaskoningDHV

N31 Traverse Harlingen | Royal HaskoningDHV

N31 Traverse Harlingen | Royal HaskoningDHV

ClientProjectbureau N31 HarlingenPeriod2012 - 2016
LocationHarlingen, The NetherlandsServicesArchitecture, landscape design, urban planning
ScopeTwo kilometre open tunnel traverse, four viaducts, a railroad viaduct and an aqueductTeamJoris Smits, Sven Spierings, Maria Selkou, Jan Brantjes