The center stack carries navigation, media, and other secondary work

What it is

The center stack (center information display) sits between driver and passenger and holds navigation, media, calls, climate, and vehicle settings—useful to driving, but not quantities that must be checked every second. It may host a slightly longer operation than the cluster, and therefore must be interruptible and usable by a passenger. Putting the master copy of speed and telltales here sends the person out of the forward view to do cluster work. The stack is secondary. It is not a second cluster.

Why it happens

Geometry writes the job: glance angle and distance from the road are larger than the cluster’s, and the hand is farther. People will pay several glances to set a destination; they will not pay the same to read speed. A next navigation act that is short and large can be sampled on the stack; full-map manipulation, playlists, and deep settings should be organized as pausable secondary tasks, not as something that stays in view. A passenger can reach this surface, so it also takes delegated work the cluster cannot. If the stack is the only source of speed and lamps, passenger use and driver sampling fight for one face.

Studying it

Place the same task (change destination, skip track, set climate) on the stack, on a touch cluster, and on wheel keys, and compare eyes-off-road and completion in motion.

Independent variables: host surface, whether a passenger can do the task, information density on the stack. Dependent variables: cumulative eyes-off-road, completion versus abandonment, whether real-time quantities placed on the stack still send people hunting on the cluster.

Watch specifically for drivers searching the stack for quantities that belong on the cluster; that is the direct signal of a broken split. Passenger completion must not enter driver eyes-off-road, but driver looks captured by stack animation must.

Where it stops holding

A tall portrait slab that reaches cluster height tempts the upper edge into cluster work and smears the split; the physical panel then needs an internal division, not a speed readout moved “because it is high enough.” Rear screens are not the stack and do not host secondary tasks for the driver. A vehicle with no stack, only cluster plus voice, moves secondary work onto voice and the wheel; it does not inflate the cluster into a stack. When parked with the brake set, the stack may take deeper settings; that is a context switch, not a cancellation of the driving split.

Applying it

• Put the main operating surface for navigation, media, calls, climate, and settings on the stack, and make those flows completable in several short glances rather than one stare.
• Let the next navigation act be sampled on the stack in large, sparse type; keep detailed map work pausable by default, not a demo that must be watched through.
• Allow the passenger to finish those secondary tasks on the stack without rewriting driving-critical quantities on the cluster.
• Verify with a list of what must be driveable from the cluster alone. Everything off that list should go through the stack or voice, and the driver should not reach for the stack to find speed.

Related

• Within the group: K6.11.1 The cluster shows driving-critical real-time information, not optional functions · K6.11.3 Secondary displays and HUDs must agree with cluster and stack, not contradict them · K6.11.4 Repeated information across screens needs a designated source of truth
• Adjacent: K6.03 Total Task Time · K6.07 Passenger and Rear-seat Interaction · K6.10 In-car Voice and Gesture
• Search terms: center stack · CID · in-vehicle infotainment · secondary task