During the primary task of driving, the main information input is visual.

The driver views the forward scene, glances to either side when necessary and also watches the rear view mirrors and instruments (mainly the speedometer). While the driver does use sound and other sensory cues, these senses play a minor role in information gathering.

The major outputs are hands and feet; the hands are used for steering control, gear changes, and operating in-car controls on the instrument panel, while the feet provide outputs for acceleration and braking.

Although obvious, it is important to recognise that the driver has a single visual resource, since the eyes do not operate independently of one another. The main implication of this is that the driver must share vision temporarily. In contrast, the driver has two hands that can perform different functions simultaneously. For example, one hand can be kept on the steering wheel while the other is used to actuate a control on the instrument panel. This redundancy in hand motion makes it possible for the driver to provide commands for vehicle control while at the same time providing commands for other in-car tasks.

However, there are occasions when hand use must be time-shared, such as when the driver makes a sharp turn and both hands are required on the steering wheel.

These simple statements demonstrate that drivers are required to timeshare vision input continuously and manual output occasionally. This helps to explain why considerable research is currently taking place to establish if gesture recognition technology can be used as a credible alternative to the existing automotive user interface.