That's why it's been bugging me in my custom hood, Rohina. I could understand if the neighborhood were crowded but it's only got eight houses so far.
I disabled 'neighborhood drift', that seemed to help quite a bit.
For anybody who ever searches this, "boolprop displayNeighborhoodRoads (True/False)" removes the roads, but not the traffic. The cars kept running on the same routes, even without asphalt.