The display (of variables whose values change rapidly) with analogue or quasi-analogue instruments is generally better and faster than digital displays. Therefore an intermediate trend towards digital displays did not see any advancement. The usage of an instrument with a conventional pointer over a display overcomes the disadvantages of a digital display and also offers the integration of subsequent functions.
Accessibility depends on the anthropometrical measurements and the type of actuation equipment. Push button switches can, for example, be situated farther away compared to devices which must be operated using the entire hand. Accessibility is described as the range which is covered by the driver in his normal seating position. The formation of the field of optimal range is somewhat asymmetrical since the movement of the left arm is constrained by the seat belt. Additionally the computer simulation, which is used increasingly, simplifies a parameter variation (angle modification, seat adjustment). The computer simulation is dealt with in the following section.
If one represents the three-dimensional view as a top and side projection for different levels, then it can be seen that the most favourable holding position for the hand is in front and a bit lower than the shoulder level, figure above. This translates to an arrangement of the hand control within a range of 100 - 450 mm above the H-point. It is apparent from the figure that the right arm has a somewhat larger range than the left arm due to the constraining of the left arm by the seat belt.
The type of operation must be coordinated with the function of the control element. Rocker switches cannot execute certain functions that have to be carried out in a discreet manner, for example, the heater. On the other hand a rocker switch is meaningful if used in the operation of the dipped headlight beam.
The area covered by the hands, without the movement of the shoulder and the upper body, is limited and for this reason not all control elements can be located within this area. For the arrangement of control elements, priority groups based on operation frequency and function, are formed.