A worker transfers GPS signals to a communication system at each node of traveling using a cellular phone terminal, and the communication system specifies the position of the cellular phone terminal and notifies positional information to a management system. When the cellular phone terminal cannot receive GPS signals or is outside a range accessible to the communication system, it starts recording acceleration data using an accelerometer. When a communicable state is recovered, the cellular phone terminal sends GPS signals and the recorded acceleration data to the communication system. A management computer determines whether the position notified by the communication system is an intended node. If the notified position is not an intended node, the management computer derives the position of the intended node using the acceleration data, and predicts the travel route based on the node position.