Victor Haydin
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What’s Really Important about Designing Human Machine Interfaces for Autonomous Vehicles?

Learn how human machine interfaces can become hallmarks of automotive brands and why automakers should encourage a user-centric approach to HMI design

April 03, 2019

7 mins read

Drivers won’t be able to communicate with autonomous vehicles (AVs) without a human machine interface (HMI). Moreover, without a proper human machine interface system design, an effective human–vehicle dialog is out of the question. So before achieving complete independence, cars should learn how to communicate their intentions to humans and do so in the most comprehensive way. As such systems develop, drivers and commuters, in turn, become more demanding. Cars should not only understand, inform, and ensure passenger safety but also entertain passengers. Let’s find out how to design an HMI system to meet the needs of both humans and vehicles.  

In this article, you’ll read about:

  • The role of HMI system design in the development of the autonomous vehicle industry
  • Five principles of human machine interface design

The design of reliable HMI systems is critical for people’s safety and AV industry growth

HMI features

What’s Really Important about Designing Human Machine Interfaces for Autonomous Vehicles?

Despite all the challenges, tech innovators and automotive companies are all agog over self-driving cars becoming a daily reality. No wonder, since according to recent research by Strategy Analytics, the autonomous vehicle industry will be worth $7 trillion by 2050. This means that automakers have golden reasons to pursue R&D for all systems required for autonomous vehicles. HMI systems are one critical component.

Automotive HMI market size will exceed $27 billion by 2024.

Report, Global Market Insights, Inc.

HMI systems are widely used in car apps to transmit vast amounts of internal and external information. Particularly in autonomous vehicles, HMI platforms are used for car-to-car communication. On top of that, an HMI is part of an advanced driver assistance system (ADAS) and helps automakers ensure a wide range of ADAS-related services. So what are the human machine interface design principles automakers and OEMs should apply while developing autonomous vehicle concepts? Let’s find out.

Read more: Learn how to build navigation software for vehicles and the critical components it should have

To leave no room for confusion, human machine interface design should be as comprehensible as possible

Since an HMI is an autonomous vehicle’s brain responsible for communication and building trust and safety, interfaces and interaction scenarios should be explicit. Today, the lack of understanding between people and cars can be annoying. But in self-driving vehicles, miscommunication can be disastrous.  

Clear and unambiguous HMI design is particularly important for level 3 autonomous driving. In lower levels of autonomous driving, ADAS features such as adaptive cruise control (ACC) and lane change assist (LCA) were the first to reflect enhancements in HMI design.

The interconnection of HMI and automated driving

What’s Really Important about Designing Human Machine Interfaces for Autonomous Vehicles?

Source: HARMAN International – Autonomous driving demands a paradigm shift in HMI development

Driving automation of any level will be put on hold until the following aspects are considered while designing human machine interfaces:

  • Passengers should know the current capabilities of a car, which features are enabled, and which are switched off.
  • Passengers should be informed if the vehicle requires them to take specific actions.
  • Passengers should be adequately informed about how the vehicle is interacting with the current driving environment.
  • There should be a standardized approach to information displayed and features enabled when switching between manual and autonomous modes.

Designing an HMI for increased usability is challenging but crucial for the future of AVs

What’s Really Important about Designing Human Machine Interfaces for Autonomous Vehicles?

One of the most challenging tasks for HMI designers is to ensure the real-world usability of a self-driving car. In a task akin to approaching the south and north poles at the same time, OEMs need to transform cars into mobile computing stations yet make them simple to drive and manage. That’s why manufacturers sometimes take a minimalist approach to HMI system design. However, this raises the next question: Which HMI elements are the minimum for safe, comfortable, and effective driving? There’s no clear answer yet.

The toughest part of designing an HMI is lack of standardization, which can lead to dangerous cases of driver confusion and errors when driving a new vehicle. Let’s take the popular automatic cruise control and lane change assist features as examples. Different manufacturers use different HMI elements to inform drivers about steering too close to the left-hand lane boundary, for instance. Consistency in human machine interface system design is critical to provide usability in AVs.

The necessity to consider a driver’s age is another delicate but vital issue with vehicle usability. In HMI design, the size and color of visual indications, sound volume, and frequency of auditory indications should vary according to the age of the driver. On top of that, the ability of modern cars to monitor the health condition of passengers and drivers should also be reflected in HMI display and interface design.

If you’re searching for a reliable vendor for the development of HMI elements or ADAS in general, contact Intellias
Get in touch

Human machine interface design should keep drivers in the loop to earn their trust

The results of two surveys regarding trust in self-driving cars

What’s Really Important about Designing Human Machine Interfaces for Autonomous Vehicles?

Source: Statista Fatal Accidents Damage Trust in Autonomous Driving

For self-driving vehicles, trust is as critical as gas is for today’s cars. Trust in the self-driving concept means confidence that the car will drive you to the destination safe and sound, act according to the driver’s expectations, and provide an enjoyable experience from high-end features. In this case, designing HMIs means designing near-absolute trust between a human and a vehicle.

Sticking to the following human machine interface design principles increases drivers’ trust:

  • Inform passengers about AV use phases (pre-use, learning, driving, etc.)
  • Inform passengers about autonomous driving events (entering vehicle, activation, manual mode, transition mode, autonomous driving mode, etc.)
  • Consider factors that affect trust like asking for feedback, informing about errors, and providing confidentiality and customization
  • Adapt HMI design elements during user interactions  

HMI systems must assure passengers that the autonomous vehicle is completely in charge of the situation and is aware of the surroundings. How should this look in practice? First, the system should be able to communicate with traffic participants. Then, the task for an HMI designer is to inform the user according to the principles mentioned earlier but avoid data overload, since it also reduces trust.

HMI system design should increase human awareness and minimize uncertainty surrounding automation

What’s Really Important about Designing Human Machine Interfaces for Autonomous Vehicles?

At each stage of human machine interface system design, we stress the importance of driver awareness. The road is not a place for surprises. Throughout the entire trip, the driver should know about the vehicle’s capabilities, receive timely warnings, and be able to monitor the road situation if vehicle or road conditions require it. A human machine interface is an effective mediator in all of these tasks.

Depending on the driving automation level, an HMI design in an autonomous vehicle should let the user monitor, recognize, and control the car to different extents. Providing clear and well-timed signals to inform a driver that the vehicle might need human interaction is a firm foundation for safe autonomous driving. Moreover, future cars should rationally interpret human responses. This includes ignoring human directions if the system identifies them as hazardous.    

Human machine interface design should provide comfort while reducing stress and adding infotainment features

What’s Really Important about Designing Human Machine Interfaces for Autonomous Vehicles?

What does comfort mean for a person in a self-driving car? First, it’s the absence of both physical and psychological stress. Second, it’s a high-end infotainment system that makes riding more pleasant. Finally, it’s a personalized user experience that makes the difference.

Similar to lack of trust, stress from driving is mainly caused by situations when an autonomous vehicle doesn’t behave the way passengers expect. A properly designed HMI won’t keep people guessing. In many cases with manual driving, the driver knows what they’ll do when a particular situation happens on the road. In autonomous driving, through voice commands and audio or visual communication, the driver should be able to ask and receive sufficient feedback about what the vehicle is going to do.

When HMI designers respect the basic need for safety, passengers can actually feel comfortable and relaxed. After that, it’s time for a personalized approach, designing the human machine interface to provide an unforgettable user experience. Take Sedric, Volkswagen’s self-driving electric concept, as an example. Sedric asks passengers to relax and invites them for a trip behind huge windows. The journey can quickly become digital, since these windows

are actually high-resolution OLED displays. This approach to HMI display design allows users to play movies, make video calls, view navigation maps, and explore other augmented reality and entertainment options.

To conclude

To design safe and comfortable HMIs, automakers and OEMs have to overcome numerous challenges and find the right approaches. It’s essential to find out how, where, and when data should be transformed into actionable information. Then HMI designers should consider when to display particular information for safe and effective communication between a vehicle, the environment, and the driver. And don’t forget about consistency in approaches to HMI design. A lack of harmonized solutions will bring confusion, which can be more than a mere annoyance since it’s driving safety we’re talking about.

Once all these challenges have been adequately addressed, autonomous vehicles will develop with a new impulse. HMI design can serve as a catalyst ushering in the future of autonomous driving.


At Intellias, we’re working on impressive autonomous driving projects and are developing HMI elements as part of ADAS feature design. If you’re interested in development of autonomous driving in general and human machine interfaces in particular, contact us to talk to one of our automotive experts.

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