PURPOSE: To obviate any accident such as a rear-end collision by a succeeding car by making a stop lamp so as to be lighted at a time when a large deceleration acts on a car as an exhaust brake and an engine brake work there.

CONSTITUTION: Both longitudinal and vertical extents of acceleration at the time of car braking are detected out of a longitudinal sensor 2 and a vertical sensor 3, thereby calculating a car's pure deceleration excluding any effect of a downward pitch from this detected value, and when this value has become more than the specified one, a stop lamp 7 is lighted.