This study examines a lane-keeping-assistance system for motorcycles by using a rider control model. By examining the computer simulation with the rider-in-the-loop system consisting of the motorcycle, the lane-keeping controller and the rider control model, the lane-keeping-assistance system suppresses the lateral displacement of the motorcycle and decreases the rider's steering torque. In addition, the virtual point regulator, which compensates the lateral displacement at the virtual point ahead of the vehicle, corresponds to not only the steering torque disturbance but also the lateral force disturbance by choosing the distance to the virtual point.