Something needs to be put into the wiki about this. When I say closed loop roads, I'm referring to a road that loops back onto itself with no junction in between. Waze can't handle this, even though they're all over the map from the basemap import, plus those that have been inserted by inexperienced editors.
The reason they don't work is illustrated below. Waze can't see them as a three-way option. As you can see in pictures 3 and 4, if they're one way against the drawn direction of the road, they can't be routed at all...note the lack of directional arrows from both ends. When they're two-way, or one-way in line with the drawn direction, Waze still sees only one option.
This is also accomplished sometimes by "helpful" editors who think that roundabouts can be used for this sort of thing, and add them to the end of cul-de-sac streets. I put a note about this on the wiki cul-de-sac page and also on the roundabout page last month, but I think this needs to be addressed somewhere, possibly on the BMEP page, or at least linked from the BMEP page. This example was a basemapped loop, which I've now removed. It's basically a cul-de-sac, but often there's a large loop like this that has multiple houses on it, and that's where the routing problems are going to really come in when Waze can't find a route away from the address, or to the address.
Streets like in my example should simply be a dead-end, since it's really a cul-de-sac. The bulb on the end doesn't add any value to the map whatsoever and will only be visible in the client at the closest zoom level, and even then, it may not appear. Larger versions of these loops, need to be broken up into two segments to get proper routing.
I'm not sure where this needs to go, or how to word it all, so I'll leave it up kentsmith and the Wiki Reorganization Team.
Illustration of the problem loop.
Only one direction available to turn.
One way against "natural direction", no turn options to get in.
One way against "natural direction", no turn options to get out.