Usability Evaluation on Tesla Model S Dashboard

8 min readFeb 16, 2021

Usability can be described as the capacity of a system to provide a condition for its users to perform the tasks safely, effectively, and efficiently while enjoying the experience. Usability engineering is a professional discipline that focuses on improving the usability of interactive systems. It draws on theories from computer science and psychology to define problems that occur during the use of such a system.

In this blog I am going conduct a complete usability evaluation referring a simulator created by Andrew Goodlad (an interactive mock-up of the Model 3 touchscreen that, although incomplete, incorporates just about everything we know about it so far).

https://projects.invisionapp.com/share/DPCUX2ETA#/screens

An acceptability Software must be acceptable to the type of users for which it is designed. This means that it must be understandable, usable and compatible with other systems that users use. We can define the overall acceptability of a computer system by the combination of Social acceptability and Practical acceptability.

Social acceptability

This model consist rear view cameras, obstacle sensors, parking assist, lane change assist, adaptive cruise control, autopilot driving and even web browsers. So Many of these features make driving a safer and more comfortable activity. These are providing a social comfort, status, reputation and moral convictions.
One of the most unique features of this model is a large central touchscreen that replaces the traditional dashboard and controls users typically find in a car. So the user can get a clear cut view of the street in a situations like reverse state. It helps to reduce the probability of accidents.
We have 2 boys (2 and 4 years old) who think it’s fun to close the FW doors, this is not always safe. Child safety only ensures that the buttons do not work when the car is in drive. This model provide a quick control to ensure child protection.

Practical acceptability

We can divide practical acceptability in several sections. Such as,

Cost: Obviously, the Tesla Model 3 probably isn’t the best car for owners on a budget. If user have the cash and access to a battery charger, would say the Tesla Model 3 is definitely worth the money.
Compatibility: The usable, compatible and understandable of this dashboard is pretty good because of a large central touchscreen and also it has a dark theme which is well suit even the environment is fully lightened.
Reliability: Overall, Tesla ranked second to last in the reliability study. It was down two spots from 2019 due to the issues identified in the Model S and the Model Y. The reason is, the problems with it’s touchscreen controls.
Support: Two years since the initial release and the Model 3 is still said by many to be the best deal in the automotive world. One of the main reason is it’s dashboard. This dashboard supports so many features which needed in this current time stamp.
Usefulness: This dashboard really useful in most cases to achieve the desired goals to the person who driving a modern car. it doesn’t take any cognitive resources away from the core task, and the functionality of this dashboard in principle can do what is needed with the use of proper design principles. The maintenance procedure is not much hard in this dashboard.

Now let’s look whether this Tesla model S dashboard follows the goals of usability evaluation.

Learnability: Users normally do not take the time to learn complete interface fully before starting to use it. But this UI really attracts the users to explore and has a proper spacing and separations between the elements. This allow users to reach a reasonable level of usage proficiency within a short time.
Efficiency of Use: The efficiency is not much satisfiable in this dashboard. The problems with it’s touchscreen controls. So the time it takes the users to perform some typical tasks are some what high.
Memorability: Because of easy learnability it’s east to remember how to use it based on the previous learning. But the categories list are shown only using icons without naming. So it’s been an impact in memorability because it’s hard to remember the icons that they used.

Few and Non Catastrophic Errors: The error rate is low in this Tesla model S dashboard. Because while performing the tasks the number of actions to perform is really low. almost all the tasks can be accomplished in 2/3 actions. Other thing is that, there is a lock option and with the use of this option we can lock the screen and avoid incorrect actions.

Subjective Satisfaction: The user satisfaction is in mixed range. If we get the negative side, I already mentioned that it has some problems in it’s touchscreen controls, in the other side it has a wide range of supports.

Heuristic evaluation is a process where experts use rules of thumb to measure the usability of user interfaces. So now let’s focus on 10 heuristics which aid evaluators in discovering usability problems under the heuristic evaluation.

Simple and natural dialogue: The UI in this dashboard is not much complex and it is a simple design with a good graphical design and color. It’ really a smart move to bring a dark theme here. Because it is well suited in any lighting conditions. When we see the overall design it gives the idea, what is it about. So it some how used Gestalt law and also spacing and highlights makes this layout more simple and natural.

Speaks the user’s language: Almost in most of the places, they used users’ language without technical terms.
Minimize user memory load: User memory load is some how high in this dashboard layout. We already understood that, the bottom navigation only contains icons. So it’s difficult to remember those things. But in the body section they used proper naming for the group of section to minimize user memory load.
Consistency: This Tesla model S dashboard is really consistent. The same information presented in the same place of the screen and dialogue boxes formatted in the same way.

Feedback: It gives continuous feedback in different places without any overlapping even any error situation occurs.

Clearly Marked Exits: In this layout almost every tasks have very few actions to complete. Therefore there is no any trap in this design and also they used back button in a place where it needs. And also the dialog box consist close button to bring the user back to previous state.

Shortcuts: To perform frequently used operations quickly, they designed several buttons with fast access without using a hierarchy of options.
Good Error messages: There were 9 error messages “park assist disabled, stability control disabled, airbag system needs service, ABS needs service, tire pressure system needs service, parking brake not set, parking brake needs attention, passenger front airbag always on, car needs service” in this system with a polite manner and without blame the user.
Prevent errors: To prevent the errors before it occurs, there is a set of messages it has which we saw before.
Help and documentation: There is a help and necessary documentation available in internet. (https://www.tesla.com/sites/default/files/model_s_owners_manual_north_america_en_us.pdf)

There are two complementary functions of evaluation. Formative evaluation is typically conducted during the development or improvement of a program or course. Summative evaluation involves making judgments about the efficacy of a program or course at its conclusion. Let’s focus on formative evaluation and summative evaluation of Tesla model S dashboard.

Formative evaluation

When we focus on the formative evaluation, while the user use street map to find a location, it uses formative evaluation and notify the user in each and every turns in the navigation.

And also it shows, still how much of time is left to end the song in a formative evaluation.

Summative evaluation

After user reach his/her destination with the use of street map feature, the box which appears to show the upcoming directions will go out and a voice message popup by indicating that the user reached the destination.

Therefore this dashboard uses both formative evaluation to evaluates the ongoing state and summative evaluations to give a conclusion at the end of the state.

There are two ways of employment test users in usability testing.

Between-subject

The Tesla model S dashboard consist so many features. But each test user only participate in a single test session. Therefore it requires a large number of test users in each condition. Because of this single test session, we need a huge individual variation in user skills. It is really a problem.

Within-subject

In here all the test users get to use all the systems that are being tested. So we do not need huge individual variation or large number of test users to perform the test cases in this dashboard.

Therefore choosing within-subject is pretty much better in this situation because of the broadness of the dashboard and we can transform a novice user to an expert user. This expertness will support a lot while the upcoming versions of this dashboard release.

Finally there are 4 stages of testing in usability testing approach.

Preparation: Planning the details of the usability testing session is, in some ways, the most crucial part of the entire process. The decisions we make at the start of the testing process will dictate the way we proceed and the results we end up with. So a proper preparation should be done before the arrival of users. eg. File created in previous test rounds should be cleared
Introduction: Brief the purpose and the procedures of the test. Such as, Not discussing it with colleagues who may be participating in future tests, in order not to bias them, Results of the test will be kept confidential, Allow users to ask questions before starting the experiment, ensure that the physical setup of the computer is economically suited for the individual user and Provide written instructions for the test.
The test itself: Here the test cases are performed. Experimental should normally refrain from interacting with the user and not provide any personal option and not indicate whether the test user is doing well or not.
Debriefing: Finally after the test, the user is deep briefed and is asked to fill any subjective satisfaction questionnaire.

REFERENCES

Usability Evaluation on Tesla Model S Dashboard

Written by Prasanth