Block length. In general, intersecting streets, determining
block lengths, shall be provided at such intervals so as to serve
cross traffic adequately and to meet existing streets. Where no existing
plats control, the blocks in residential subdivisions should not exceed
1,800 feet nor be less than 400 feet in length, except where topography
or other conditions justify a departure from this maximum. In blocks
longer than 800 feet, pedestrianways and/or easements through the
block may be required near the center of the block.