A vehicular, adaptive brake light to custom light sequencing system generally includes an OEM vehicular brake light circuit electrically connected to OEM brake lights of a vehicle, and an aftermarket flashing circuit electrically connected within or to the OEM vehicular brake light circuit to cause the OEM brake lights to flash. They system further includes an aftermarket directional indicator circuit electrically connected within or to the OEM vehicular brake light circuit and electrically connected to the aftermarket flashing circuit to effectuate a flashing of at least one of an OEM left brake light and an OEM right brake light. The system also includes an aftermarket hazard light circuit that is electrically connected within or to the OEM brake light circuit and to the aftermarket flashing circuit to effectuate a flashing hazard by the OEM brake lights.