1. Tunnel under single-lane roundabout outside town
Dronten, N23, tunnel under roundabout outside town. The new N23 will be connected to the existing N307 near Dronten by way of a roundabout. In order to create a safe route to the schools a bicycle tunnel will be constructed underneath the roundabout and part of the tunnel will be cut away at the same time.
2. The new N23
Between Lelystad and Dronten the N23 (N23 = Road number provincial road) will be constructed at the same time as and next to the Hanze railway line. Near Dronten the N23 will be connected to the existing Dronterringweg (N307). The N23, as a road outside town, will have a speed limit of 80 km/h.
3. School route intersects roundabout
Between Swifterbant and Dronten large numbers of school-age children use the separate bike path along the N307 daily. In the near future traffic intensities on the N23 will be approx. 20,000 mv/24h. Thanks to the bicycle tunnel cyclists may cross the N23 conflict-free, ensuring the continued existence of the direct and safe route.
4. Design of the roundabout
The separate bike path along the N307 will pass underneath the roundabout with the aid of two tunnels. The bike path to the future industrial estate will cross the new entrance road at ground level. As the roundabout is outside town, cyclists will have to yield to motorised traffic here. Construction of the roundabout will cost 350,00 Euro, of the tunnel 800,000 Euro.
On both sides the gradient will be 4%, in accordance with directions. The difference in height is approx. 3.50 metres.
6. Two short tunnels
As a result of the large radius of the roundabout (25 metres) the bike tunnel would have to be approx. 80 metres long. For social safety reasons this is undesirable. In order to create a more open atmosphere the decision was made to open up the tunnel in the middle of the roundabout.
To prevent motorised vehicles from entering the tunnel, railings will be erected around the traffic island and next to the ramps of the bicycle tunnel.