30 km/h zone
A designated area where the speed limit is set to 30 kilometers per hour, often in residential or school zones.
This residential area is designated as a 30 km/h zone.
In 30 km/h zones, pedestrian-priority rules are strengthened.
Kanji numeral variant; less common but still seen in some contexts.
Borrowed from English 'zone 30', a traffic engineering term adopted in Japan for residential speed management.