Patent ID: 7548173

Claim:
A vehicle on-board unit comprising: a vehicle traveling condition detecting section configured to detect at least one vehicle traveling condition indicative of a potentially inadequate safety zone occurring in a host vehicle equipped with the vehicle on-board unit, with the vehicle traveling condition detecting section monitoring a host vehicle location as part of the vehicle traveling condition to determine a travel lane of the host vehicle using a plurality of detection results of the host vehicle location; an automatic brake light triggering section configured to output a brake light activation signal upon determining a predetermined condition has been satisfied based upon the vehicle traveling condition detected by the vehicle traveling condition detecting section, the automatic brake light triggering section adjusts the predetermined condition used to determine when to output the brake light activation signal depending upon the travel lane; and a brake light activating section configured to activate brake lights of the host vehicle without performing a braking operation in the host vehicle upon receiving the brake light activation signal from the automatic brake light triggering section.