OpenStreetMap
I edited http://www.openstreetmap.org/?lat=52.348465&lon=4.918406&zoom=18&layers=M
The Wibautstraat / S112 going south is crossing the roundabout, and you are not supposed to turn onto or off the roundabout on the north side - there are other ways to get on or off the roundabout.
I first tried a crossing with turn restrictions, and 2 ways crossing without a bridge is often seen as indicative of an error. But I get a node woth a small traffic sign, and I do not see that often on OSM. So I decided for just having the ways cross without an intersection. Is that the right way?
Discussion
Comment from Vclaw on 14 December 2011 at 21:56
I assume the roads cross at the same level, ie there isn't any bridge or tunnel?
If so, then the ways should cross with a shared node at the intersection.
And you should add turn restrictions, to specify that you are not allowed to turn off. Yes, Potlatch will show this with a little road sign symbol.
Its true you don't see that often in OSM, but that's because not many turn restrictions have been mapped yet (this will probably vary by area, there may some places with lots of turn restrictions mapped).
Comment from jutezak on 15 December 2011 at 21:52
I tried recreating the shared node (worked) and adding a turn restriction.
Adding the restriction worked, but I couldn't assign the directions it applies to, as no street names appeared in the potlatch menus. They did before. For now, I have left the map without the shared node.
Comment from Vclaw on 15 December 2011 at 22:50
You need to split both of the ways at the intersection node. ie select that node, then click the little scissors icon.
Then you should be able to set the streets for from and to.
Comment from jutezak on 15 December 2011 at 23:19
Yup, that worked. Thanks.