The invention relates to a control device for affecting the accelerator (15) of a vehicle by means of a an actuator, typically a handle (3), arranged within the reach of the driver. The main purpose of use of the invention is to modify vehicles equipped with foot pedal control means so that they become better suitable to be used by disabled persons. The invention is suitable to be used by professional drivers to improve driving comfort. According to the invention, the control device comprises means (20, 21, 30, 20, 60, 30, 20, 80, 30) for locking the actuator (3) with a margin for adjustment into a position in which the actuator (3) is utilized to affect the accelerator (15) of the vehicle, and means (22, 25, 60, 22, 25, 81) for producing a margin for adjustment in said position locked with a margin for adjustment, which margin for adjustment allows the driver to move the actuator (3) and to adjust the accelerator (15) within the adjustment range (31) of the margin of adjustment without releasing said locking. Furthermore, the control device according to the invention comprises means (20, 21, 30, 20, 60, 30, 81, 30) for automatically releasing the locking with a margin for adjustment when the driver turns the actuator (3) more than is allowed by said margin for adjustment.