A driving assistance method for assisting driving of a mobile machine, the driving assistance method includes: executing processes of, by one or more processors, acquiring at least one of a first position on an autonomous driving route and a first angle indicating a direction in which the mobile machine travels at the first position when the mobile machine deviates from the autonomous driving route by switching from autonomous driving to manual driving, and outputting driving assistance information for assisting the manual driving according to at least one of a difference between the first position and a second position that is a position of the mobile machine traveling by the manual driving, and a difference between the first angle and a second angle indicating a direction in which the mobile machine is traveling at the second position.

An operation system performs autonomous operation by using an operation server for an autonomous driving vehicle. The operation server includes a memory unit containing three-dimensional map data. An autonomous driving vehicle connects to the operation server via a wireless network. A vehicle control unit creates a traveling route based on the map data received and, when an elevator of a building is to be used, creates elevator usage information and elevator control information, including the boarding and exiting floors. The elevator is equipped with an elevator control unit that is connected to the operation server to control ascending and descending of an elevator cage. A control unit of the autonomous driving vehicle transmits the elevator usage information and the elevator control information to the elevator control unit. The elevator control unit gives a voice announcement from a voice output unit in the elevator cage.