In geomantic omen, the north-south alley is wide in the north and narrow in the west. What's the point?

This question is rather general. The people on the side of this alley are different from family to family. Building structure will affect, ground elevation will affect, orientation will affect, and indoor layout will affect. Every point has an influence on Feng Shui. . . The description of an alley alone can't give the correct answer.