In one embodiment, the invention describes a method of providing advance braking warning before an ADV reaches a point where the ADV is expected to brake. The method enables brake lights to be turned on before actual braking occurs, thus providing trailing vehicles more time to respond. According to the method, a trajectory is generated at a starting point. The trajectory includes a number of discrete points that the ADV is to follow. One or more discrete points are identified from the number of discrete points where the ADV is expected to brake based on previous driving statistics and calculated decelerations. At a predetermined time prior to reaching each of the identified discrete points, the ADV can turn on its brake lights to warn trailing vehicles that the ADV is about to brake so that the trailing vehicle can start to respond earlier.