In this research, a methodology to assess the Operational Design Domain of Lane Keeping Assistance System equipped vehicles is developed. The method is mainly intended for use by manufacturers of semi-automated vehicles to assess the situations and conditions in which their lane keeping systems that are already available in the market, can and cannot perform. The methodology is implemented to a real-road case study using an instrumented Tesla Model S and assesses its Autosteer system at certain pre-specified situations. It involves assessment of the situations based on three main components: lane keeping performance of the system in these situations; the lateral objective risks of driving in these situations; and the driver’s attitude/behaviour using questionnaires at three stages of testing.