A server includes: a candidate trajectory generation part for generating a candidate traveling trajectory of a target vehicle; a trajectory simulator for executing a trajectory simulation on the candidate traveling trajectory generated by the candidate trajectory generation part; a trajectory evaluation part for determining a traveling trajectory based on a result of the trajectory simulation; a vehicle coordination part for transmitting information of the traveling trajectory determined by the trajectory evaluation part to an onboard device; an infrastructure coordination part for obtaining sensing information from an infrastructure sensor; an ambient environment generation part for generating information indicating an ambient environment of the traveling trajectory, based on the sensing information obtained by the infrastructure coordination part; and a resetting determination part for determining whether to reset the traveling trajectory.