Abstract: An accident avoidance system in which a substantially continuous data stream consisting of multiple vehicle velocity and location information is processed by means that will generate advisories to vehicles that are approaching potentially hazardous situations. These advisories are in advance of the vehicles hazard encounter so that driver corrective action can be taken to avoid collision. For each vehicle along a monitored length of highway, means are provided for computing the vehicles actual acceleration or deceleration and for computing the deceleration required for the vehicle to avoid an accident. Collision avoidance advisories are generated whenever the vehicle's acceleration or deceleration deviates from the deceleration required to avoid a collision. Means are provided for detecting vehicles that may be operated by drivers whose performance is impaired.

Abstract: An interrogator-transponder system in which multiple vehicle mounted transponders which may be closely spaced in distance and moving at similar velocities are interrogated by interrogation signals that are identical for all interrogations. Digital coded data blocks consisting of an address code and a message code are transmitted on the interrogation frequency and are interleaved with the interrogation signals. Transponders respond with a coherent identification code and a message data code signal that is displaced in frequency from the interrogation signal by an amount that is identical for each transponder. The transponders decode interrogator data blocks that are associated with an address that is identical to the transponder identification code. The response signal spacings in time are difference for each transponder but are always multiples of the pulse repetition interval of the interrogation signal.

Abstract: An interrogator-transponder system in which multiple vehicle mounted transponders which may be closely spaced in distance and moving at similar velocities, respond with a coherent identification code signal that is displaced in frequency from the interrogation signal by an amount that is identical for each transponder. The response signal spacings in time (Pulse repetition intervals) are different for each transponder but are always multiples of the pulse repetition interval of the interrogation signal. A coherent reference for the received transponder codes is obtained by combining the coherent interrogation signal with a coherent reference that is substantially identical in frequency to the displacement frequency of the transponder response signal.Means are provided in the interrogation device to determine the velocity of each transponder and its range with respect to the interrogator and to identify vehicles with inoperative transponders.

Abstract: An interrogator-transponder system in which multiple vehicle mounted transponders, which may be closely spaced in distance and moving at similar velocities, respond to an interrogation signal in a sequential or random sequential manner so as to reduce response signal interleaving to an acceptable level. The response signals include a vehicle identification code and are processed by the interrogator to yield data, for example, on specific vehicle speed, distance from the interrogator, vehicle wanted for investigation, and vehicle with an inoperative transponder.