A new procedure is described for measuring realistic on-the-road vehicle directional response characteristics. Conventional control system analysis techniques are used in the procedure to derive the transfer function relating steer input to vehicle lateral motion. The influence of the driver's limited torque capabilities on the steering system input is introduced in a nontraditional, though direct, manner. This approach produces somewhat different descriptions of vehicle response than have been obtained in the past, when such descriptions did not include this driver influence. Since the resulting transfer function is a unique on-the-road description of the vehicle dynamics, realistic vehicle motion response to any quantifiable steer input can be computed. This procedure offers the additional benefits of test procedure simplicity and minimum test road facility requirements.