advertising van; loudspeaker truck
A vehicle, often a van or truck, fitted with loudspeakers and used to broadcast advertisements, political messages, or public announcements while driving around.
During election season, loudspeaker trucks drive around town repeatedly calling out candidates' names.
商店街を宣伝カーがゆっくり走りながら、特売の案内を流していた。
An advertising van was slowly driving through the shopping district, broadcasting information about a special sale.