To facilitate an appropriate countermeasure to crew members of a vehicle when an abnormal situation related to an on-vehicle apparatus occurs.

In this on-vehicle system, the on-vehicle apparatus 10 mounted on a vehicle for communicating with a roadside apparatus installed on the road side in a turnpike road electronic toll collection (ETC) system is connected to a navigation apparatus 20 mounted on the vehicle so that they can communicate with each other. The on-vehicle apparatus 10 reports to the navigation apparatus 20 an error code indicating the kind of an abnormal situation occurred when the abnormal situation related to the on-vehicle apparatus 10 has occurred. On the other hand, the navigation apparatus 20 stores a message for showing how to cope with contents of the respective error codes or errors in a storage part 23 and displays to a display part 27 the message associating with the error code reported by the on-vehicle apparatus 10. Thus, contents of the occurred error and a method of coping with them can be understood instantly by the crew members of the vehicle.