A vehicle system, including: an on-board device mounted on a vehicle; and a control device configured to control the on-board device such that the vehicle travels in a target traveling state, wherein the control device includes: a predicting portion that predicts a state of the on-board device when the vehicle travels in the target traveling state; and a modifying portion that modifies the target traveling state when the control device determines based on the state of the on-board device predicted by the predicting portion that an operation of the on-board device needs to be limited.