noun
national expressway; national motorway
A legal term defined in Japan's Road Act for high-speed, limited-access national highways. In everyday language, people more often say 高速道路.
高速自動車国道は、全国的な自動車交通網を形成する道路です。
National expressways are roads that form a nationwide automobile traffic network.
The common, everyday term for any expressway or motorway. 高速自動車国道 is a specific legal category within the broader 高速道路 system.
Compound of 高速 (high-speed), 自動車 (automobile), and 国道 (national road). The term is defined by Japanese road law.