Waze currently routes by finding the fastest route, considering both the expected travel time and certain penalties. For example, navigating onto a private road adds a 2-hour penalty to the route, effectively forcing travel around that segment unless there is no other route.

My suggestion is that all segments have a Penalty attribute that editors can set in WME. Used thoughtfully, this penalty attribute could give the routing engine a nudge away from areas where, based on editors' local knowledge, traffic should generally not be sent.

For example, if all the segments into a residential neighborhood were assigned a 5 minute penalty, then routing would tend to stay on the main streets. BUT if there was a closure or serious delay on a bordering thoroughfare, then the small penalty would be overcome and (temporary) routing through the residential neighborhood would still be possible.

Of course it is possible to "hack" this feature using Private Road segments, but (a) that doesn't conform to community standards for editing and (b) it forecloses the ability to use those streets for detours when there is a serious delay or closure elsewhere in the grid.