See this section in the Wiki.
In order for the Waze Application to properly route from a location on a cul-de-sac or dead-end road, the end of the last segment must have an end-node. Without this end-node, Waze will give the instruction Proceed to Highlighted Route.
You can edit the road or post a note in the Map Editing forums ((Update Requests) to have someone look at it.
