noun
advertising truck; billboard truck
A truck or van equipped with loudspeakers or large signs, used for commercial advertising or political campaigning.
選挙期間中、街中を広告宣伝車が走り回っている。
During the election period, advertising trucks drive around the city.
あの広告宣伝車は新製品の音楽を大音量で流している。
That advertising truck is playing music for a new product at high volume.
街宣車 specifically refers to a vehicle used for street propaganda, often by political groups, while 広告宣伝車 is broader and includes commercial advertising.
Compound of 広告 (advertisement), 宣伝 (propaganda/publicity), and 車 (vehicle).