Minecraft wiki entry for Building_a_metropolis, associated text: Suburban street:
Recommended material: Stone, cobblestone, or stone bricks.
1-2 lanes equivalent, a small sidewalk or possibly not, purely houses nearby. Can be up to 1/3, or possibly even 1/2 slope. Should do as little earth-moving as possible and doesn't need to be very efficient as a through street. Typically 3 to 11 blocks wide.