In built-up areas, the widening of existing narrow roads into 4m required by the Building Standard Law 42-2 hava become increasingly difficult. This paper first observes the status quo of a typical built-up narrow street area in Sumida-Ku. Then, to this area, a hypothesis is applied,namely:1,Not all the roads have to be widened to 4m.0nly the roads forming a 50m grid in the area needs to be widened. 2,By considering the block's total condition, other roads' width is sufficient with 3m. It is demonstrated that the block's fire-preventing qualities remain sufficient under this hypothesys. which also proves to be much more applicable to the existing conditions.
