Vehicle Control Device, Vehicle Control Method, and Vehicle Control System

The vehicle control device, independently of acceleration and deceleration operation by a vehicle driver, adjusts a vehicle speed to a predetermined target vehicle speed or adjusts an inter-vehicle interval between the vehicle and a preceding vehicle which travels ahead of the vehicle, to a predetermined target inter-vehicle interval. The vehicle control device obtains information concerning the inter-vehicle interval between the vehicle and the preceding vehicle and information concerning acceleration and deceleration operations by the driver, to update settings of the target vehicle speed and the target inter-vehicle interval according to the obtained information concerning the inter-vehicle interval and the acceleration and deceleration operation. Furthermore, the vehicle control device outputs, to a braking/driving device (a brake pedal and an engine) of the vehicle, a braking/driving command (a driving command and a braking command) for adjusting traveling state based on the updated target vehicle speed and target inter-vehicle interval.