The effects of age, viewing distance, arrangement of switches and display form on performance to design of display and control systems friendry to older adults were discussed. A dual-task experimemt was conducted in which the primary task was first-irder tracking. The secondary tasks included control of an air conditioner, the operation of a radio, and the operation of a CD/MD, by means of a steering wheel mounted swich. The switch was either vertical or cross arrangement. In both-hands switch arrangement condition, the operation was carried out with two hands using both left vertical switch and right cross switch. In one-hand swith arrangement condition, the operation was carried out with only one hand using either left or right cross switch. The display was arranged in front of a participant. The display form was either left or right display. The viewing distance conditions were 60, 80, and 100cm. When the right display form was used, both one-hand (using only right cross switch) were selected. When the left display form was used, both one-hand (using only left cross swith) and two-hand arrangements (using both left vertical and right cross switch) were selected. As predicted, age affected the performance measures ( percentage correct, task completion time, and tracking error). The viewing distance also affected performance (percentage correct), Both display form and switch arrangement also affected performance (task completion time). Such results should be taken into account when designing display and control systems in man-vehicle systems.