A vehicle safety device for warning persons in traffic has an antenna unit having at least a first antenna, a second antenna, and a third antenna. The antennas are mounted spaced apart from each other in a predetermined spatial relationship at predetermined positions on a vehicle to be safe-guarded. Each antenna generates an electromagnetic field. The vehicle safety device also has a control unit in electrical communication with the antenna unit, which defines a warning zone for the vehicle and determines whether a warning module matched to the antenna unit is located within the warning zone.