US Patent 10144349 Collision avoidance system and collision avoidance method

A driver state detection unit is configured to detect a state of a driver of a host vehicle. An environment detection unit is configured to detect an environment in which the host vehicle is traveling. A time setting unit is configured to set a predetermined time period on the basis of the detected environment. An external warning device is configured to perform an external warning operation that warns another vehicle traveling in the vicinity of the host vehicle. When a time determination unit determines that the predetermined time period has elapsed, an internal warning device is configured to perform an internal warning operation that warns the driver of the host vehicle.