noun
narrow back road (under 4m wide)
Legal/administrative term for a road narrower than 4 meters, often used in urban planning or traffic regulations.
この地域には細街路が多く、消防車の進入が難しい。
This area has many narrow back roads, making it difficult for fire trucks to enter.
細街路では一方通行の規制がよく見られる。
One-way traffic restrictions are common on narrow backstreets.
狭い道 is a plain description of any narrow road, whereas 細街路 is a technical term used in official contexts.
Compound of 細 (narrow) + 街路 (street, road). The term is used in legal and administrative contexts to define roads narrower than 4 meters.