The PACMAD model notes 7 attributes that impact usability. For this particular interface, I would reorganize the attributes in the order of their significance in this context:
- Cognitive load: this is a very important concept when it comes to an in-vehicle touchscreen display. Unnecessary cognitive load from this dashboard device can cause great bodily harm to both the drivers, passengers, and other vehicles on the road. It is essential that the app is as cognitively lightweight as possible. This dashboard should have hands-free capabilities and minimize the amount of interaction required to take action. In the case of a touchscreen display, providing other affordances by which a user can take action on the interface would be ideal. It should not be a mystery when action is taking place.
- Learnability: This interface needs to be incredibly easy to learn. Chances are, a driver will take little to no time prior to hitting the road to use this interface. It is very important that the commands are easy to use, and that the interface feels like a natural extension of interactions that would already occur while the vehicle in use. A user should not have to stop and think about how to instruct the interface to take a command.
- Efficiency: This interface needs to allow the user to efficiently interact with it. It should require the least amount of interaction to yield the greatest amount of information. It should aim to minimize clicks and decision points unless absolutely necessary. It should minimize the amount of steps required to achieve a task as well.
- Errors: Errors can be infuriating for drivers who are stuck in traffic or have agitated passengers with them. The ideal interface would minimize user error as much as possible, and provide simple ways for the user to correct those errors if so. A lot of error management can be uncovered through usability testing and ideally would be mostly worked out before going live.
- Satisfaction: Users should not be openly frustrated or agitated with this interface. It will most likely distract them from their primary action of driving safely on the road. Satisfaction can also result from being able to quickly achieve multiple tasks during the same trip.
- Effectiveness: In order for this interface to be effective, it must solve a problem for the user in a better way than any other interface currently on the market. The product managers, developers, and designers need to consider what is currently being done in the market to solve these kinds of problems, and to ensure that they are putting out an even better product. A copycat product adds to the noise of the marketplace and does not actually serve the user.
- Memorability: If the interface is learnable, efficient, minimizes errors while maximizing satisfaction, it should also be memorable so that if they don’t use this interface daily, they can always pick up where they left off. It should be easy for drivers of all walks of life — with different driving patterns, different accents, different reach distances — can use the interface with the same amount of ease and muscle memory.