A vehicle on-board unit is configured to communicate with other vehicles to increase an accuracy of a lane centerline determination of a road that the vehicle is traveling. The vehicle on-board unit basically has a vehicle path history generating section, a two-way wireless communications section and a lane centerline determining section. The vehicle path history generating section generates a host vehicle path history data indicative of a travel path of the host vehicle. The two-way wireless communications section receives a preceding vehicle message that at least includes a preceding vehicle path history data indicative of a travel path of the preceding vehicle along a lane that the host vehicle is currently traveling. The lane centerline determining section determines a lane centerline of the lane that the host vehicle is currently traveling based on the host vehicle path history data and the preceding vehicle path history data.