Experiments were carried out to determine the ability of drivers to detect changes in several vehicle characteristics which affect the "handling" of the vehicle. The experiments determined these just notice-able differences for vehicle response time stability factor and steering ratio. They show a very high differential sensitivity to changes of response time and reasonable good ability to detect changes of steering ratio and stability factor. There are great differences between the discriminatory ability of different subjects and also within the same subject on different occasions The "constant stimuli" and up-and down methods were used in establishing the JND's. The magnitude of the time interval between presentation of the standard and comparison vehicles and the speed at which the test was made also defected the magnitude of the just noticeable difference.
Abstract