I believe it's not an in- versus out-group issue as such. The issue is that the number of locals is a tiny fraction of the number of outsiders passing through,

I believe it's not an in- versus out-group issue as such. The issue is that the number of locals is a tiny fraction of the number of outsiders passing through, leading to a vast increase in traffic on the formerly quiet street. When only locals who lived on or near the street knew about the route, you might see five cars a day cutting through. Now that Waze is onto it, they're seeing five cars a minute cutting through.