The A31 / N31 is a motorway and an expressway in the Netherlands. It connects the A7 near Zurich with the A7 near Drachten, passing close to Leeuwarden, the provincial capital. It is slightly unusual due to it changing from full motorway to normal 2-lane road along various sections of its 65 km length.
Map of A31, Netherlands
The short section between the Zurich interchange with the A7, and exit 15 for Zurich (approx 1.7 km) is designated as the A31 and is built to motorway standards. The next 7 km continues as a 4-lane expressway, until the road narrows to just a normal 2-lane road for the next 3 km while it passes over an elevated section through Harlingen. This section from Zurich to Harlingen is designated as the N31, but retains the motorway-style grade separated intersections. For the next 18 km, until exit 22 for Marssum, the road is once again designated the A31 and is built to motorway standards. This section of the A31 bypasses the towns of Franeker and Dronrijp. At exit 22 one has to take this exit to follow the N31 while continuing over the exit, the road reverts to an expressway and continues as the N383 into Leeuwarden.
The remaining 35 km of the N31, until it meets exit 30 of the A7, is once again an expressway. Of this last section, the first 13 km around Leeuwarden is a just a 2-lane road with at-grade intersections and utilises traffic signals and roundabouts, while the final section opens out into 4-lanes with grade separated intersections. The widening of this last section to four lanes, was completed in 2008.
The entire route is in Friesland Province.