Abstract: A passive warning system for communicating vehicular deceleration and other information through a warning light. A microprocessor-based warning system according to the invention accounts for variations in vehicular speed and ambient driving conditions in generating a warning signal having an intensity or blinking rate related to a rate of deceleration. The microprocessor is also programmed to measure deceleration more frequently as the speed of the vehicle increases, allowing information to be communicated in a timely manner. In one embodiment of the invention, the microprocessor is programmed to maintain the highest intensity warning signal activated for a predetermined period of time in order to inform other vehicles of an earlier speed reduction. Further, a warning system according to the invention can be configured to communicate a high intensity warning signal if the wheels of the vehicle become suddenly blocked or rotate at a rate that is disproportionate to the speed of the vehicle.