An automatic braking system for automotive vehicles is described. The system employs an onboard radar sensor to measure distance and relative closing velocity to obstacles in the vehicle path. This range and range-rate information is processed to generate a control signal which is a measure of the critical braking level existing in the dynamic environment. In response to selected control signal thresholds, the system provides the driver with advance warning of potential collision situations and can subsequently automatically apply vehicle braking if the driver response to the warning is judged inadequate. The critical threshold at which automatic braking is activated is selected to be well beyond that of a normal alert driver, thereby allowing him time to exercise his own options.Problem areas associated with practical implementation of the automatic braking system on the production automobile are discussed.Approaches to the problem of similarly equipped vehicles mutually interfering with each other consider controlled radiation, modulation, and signal processing techniques. All-weather performance is discussed in terms of radar operating frequency and road surface conditions. The problem of false alarming on off-path nonhazardous objects typified by signs, bridges, and other lane traffic is treated with respect to suppressing false alarms while maintaining adequate detectability and performance response on true obstacles. System-driver interface considerations and related human factors are discussed in terms of impact on system design and operational philosophy.