A server comprising: an infrastructure linkage unit that has a function of communicating with an infrastructure sensor which is installed in the vicinity of a road that generates sensing information about an obstacle point at which an obstacle exists on a road, the infrastructure linkage unit acquiring the sensing information from the infrastructure sensor; an affected vehicle identification unit that identifies a vehicle that is affected by the obstacle, among a plurality of vehicles, as an affected vehicle; a passing ability determination unit that determines whether the affected vehicle is capable of passing by the obstacle, based on a vehicle width of the affected vehicle and a passable width of the road at the obstacle point based on the sensing information; a route designing unit that designs a detour route on which the affected vehicle travels to avoid the obstacle point, when the passing ability determination unit determines the affected vehicle is not capable of passing; and a vehicle linkage unit that has a function of communicating with an in-vehicle device installed in the affected vehicle, the vehicle linkage unit transmitting information about the detour route to the in-vehicle device, wherein the vehicle linkage unit further transmits to the in-vehicle device, a command causing transmission of the information about the detour route to the other vehicle by using an inter-vehicle communication function which is adapted to communicate with another vehicle, which inter-vehicle communication function is provided in the in-vehicle device to communicate with another vehicle, wherein the passing ability determination unit determines a vehicle control width required for controlling the affected vehicle, and determines whether the affected vehicle is capable of passing by the obstacle, by comparing the passable width with a value obtained by adding the vehicle control width to the vehicle width, wherein the route designing unit designs the detour route with a road provided with the infrastructure sensor prioritized. an infrastructure linkage unit that has a function of communicating with an infrastructure sensor which is installed in the vicinity of a road that generates sensing information about an obstacle point at which an obstacle exists on a road, the infrastructure linkage unit acquiring the sensing information from the infrastructure sensor; an affected vehicle identification unit that identifies a vehicle that is affected by the obstacle, among a plurality of vehicles, as an affected vehicle; a passing ability determination unit that determines whether the affected vehicle is capable of passing by the obstacle, based on a vehicle width of the affected vehicle and a passable width of the road at the obstacle point based on the sensing information; a route designing unit that designs a detour route on which the affected vehicle travels to avoid the obstacle point, when the passing ability determination unit determines the affected vehicle is not capable of passing; and a vehicle linkage unit that has a function of communicating with an in-vehicle device installed in the affected vehicle, the vehicle linkage unit transmitting information about the detour route to the in-vehicle device, wherein the vehicle linkage unit further transmits to the in-vehicle device, a command causing transmission of the information about the detour route to the other vehicle by using an inter-vehicle communication function which is adapted to communicate with another vehicle, which inter-vehicle communication function is provided in the in-vehicle device to communicate with another vehicle, wherein the passing ability determination unit determines a vehicle control width required for controlling the affected vehicle, and determines whether the affected vehicle is capable of passing by the obstacle, by comparing the passable width with a value obtained by adding the vehicle control width to the vehicle width, wherein the route designing unit designs the detour route with a road provided with the infrastructure sensor prioritized.