The ever-increasing reliance on touch screens in cars is a controversial topic. With each new product release, the comment sections of articles and youtube videos are filled with negative remarks. Yet, carmakers are totally committed to the race of creating ever-bigger screens. If public opinion is so against touch interfaces in cars, why do car companies use them? I dove into this topic and confirmed my hypothesis: touch screens are not the problem per se, but car companies' design execution is.
How We Got Here
Touch screens in cars are not new. In fact, the first production car fitted with a touch screen was the 1986 Buick Riviera.
The CRT touch display was not that bad, but it took some decades before touch screens were good enough to be widely adopted in cars. After Tesla launched the Model S with its 17" touch screen, carmakers have been eager to design increasingly bigger touch screens. Today, it is an exception if a car is not fitted with one. There are many reasons why this is happening. To dive into those, we first have to define the different types of interactions that occur while driving and how they evolved over time.
Classifying the Interactions
Aside from the essential driving controls, like steering and braking, I split the interactions into three groups. The first set is the primary interactions. They include all the functions that are directly related to driving and safety. Examples are monitoring the speed, turning on the indicators, and operating the windscreen wipers.
The secondary interactions are actions that occur frequently but take little time to accomplish. These can be changing the music volume, changing cabin temperature, or turning on the airconditioning.
The tertiary interactions are the opposite of the secondary ones. They are infrequent but require a high cognitive load and take longer to accomplish. Examples are filling in a destination in the navigation system or changing personal settings in the car.
The Evolution of the Interactions
Over time, these sets of interactions have evolved in mostly the same way. The interior of the Volkswagen Golf is an excellent demonstrator. The first generation Volkswagen Golf has a simple interior. The primary actions are limited to two gauges, some buttons, and a stalk for the indicators. The same goes for the secondary settings, consisting of three sliders to control the temperature and some volume controls. The only tertiary interaction is to find and set a radio channel.
Over the years, you can clearly see the impact of innovation on the interactions. With each generation, more features are added to the interior.
All three sets of interactions increase in quantity, even the primary ones. In the Golf, for example, instead of some basic gauges and controls, the latest generation's primary interactions now also include adaptive cruise control, speed limit warnings, and a range of other safety systems. Even something as simple as turning on the windscreen wipers or lights has increased in complexity with different modes, sensors, and settings.
Similarly, the secondary controls include countless different ways to set the right cabin temperature. There are buttons for heated seats and windows, airconditioning, individual climate control, and more.
But the real visible change is an exponential increase in tertiary interactions. Whereas in the first generation Golf, you can only choose a radio station, today there is an endless list of radio channels, streaming services, and podcast platforms. And that is just the media. Almost all cars come with navigation systems, phone connections, and internet-connected apps. All of these can be set up and configured to fit your personal taste. For example, you can choose the exact color of the interior lights, how heavy the steering should be, and which information should be shown in the cluster display.
Initially, all these interactions were controlled via indirect, physical controls. But over time, with each generation, the display grows in size, and the number of physical controls decreases.
The latest generation Golf is another important step because even the secondary interactions are not moved to the touch interface. Most of the physical buttons that remain are the ones that are legally required.
Why Choose for Touch Screens?
In 2001, BMW launched iDrive, one of the first in-vehicle infotainment systems. It was designed around indirect interactions via a controller close to the gear lever. At the time, it was a good balance between available technology, cost, and usability.
Over time, just like most in-car infotainment systems, BMW adjusted iDrive for use with touch interaction as well. Why did they decide to include touch interaction in the later version?
A lot of it has to do with the increasing complexity of tertiary interactions. As the number of these interactions increases with each generation, indirect controls seem to perform worse than touch interaction, especially in two areas: task completion time and adoption.
Research has shown that tertiary tasks are performed significantly faster via touch interactions when compared to indirect controls 1. Even compared to other possible interaction techniques like gesture interaction and voice interaction, touch interaction performs equal, if not better 2.
Naturally, task completion time is only one way to measure the success of an interaction model. Touch screens score differently when it comes to visual attention, lane deviation, reaction time, and others. Carmakers have to weigh the time it takes to complete the tasks versus the gravity of the distraction. In a lot of scenarios, touch interactions are the preferred method.
The second solid argument is the adoption rate of touch interfaces. Once drivers enter their cars, their focus is on driving and not on learning a new system. So one way to decrease driver distraction is to make the interaction as close to other familiar digital products as possible. As such, touch screens are preferred over indirect controls.
The next reason why car makers use touch screens has to do with decluttering. It is a term that is often heard in design departments. It means to reduce the visual overload or perceived complexity of the interior. Getting into a car and seeing a dashboard full of buttons gives a busy, overwhelming look. Instead, a calm-looking interior with few buttons has a positive impact on comfort and perceived quality.
Additionally, many customers relate a big touch screen to a technologically advanced car. As an interior designer, you don't want your car to be perceived as old-fashioned so fitting a giant screen shows your brand is futuristic.
Compared to a dashboard full of different buttons, knobs, and screens, a single touch screen is a much more straightforward part to design, spec, and maintain. Therefore, carmakers may prefer to fit a standardized touch screen instead of a range of custom buttons and knobs because of the development cost. Another advantage is the possibility to modernize the interior of the car by updating the UI design. Digital design trends move much faster than interior design trends. Tesla has shown that updating the interface of the Model S helps to delay an expensive redesign or new model introduction because the car looks less outdated.
Disadvantages of Touch Screens
Design-wise, the main arguments in favor of touch screens are task completion time and adoption. But there are plenty of ergonomic downsides.
In mobile environments, like cars, the users' primary focus is on controlling the vehicle. So touch interfaces not only have to be usable and accessible, but they also have to ensure road safety. As discussed before, even though task completion time is the fastest with touch interaction, there are other driver distraction measures where touch interaction is not the preferred method.
One of those is visual attention. When interacting with a touch screen, drivers need to move their visual attention from the road to the screen to find the object they want to select. Furthermore, they have to coordinate their finger to that object without any tactile objects guiding it. With physical controls, much less visual attention is needed to perform the interaction, leading to less distraction 3. What is the impact of this difference in visual attention between touch controls and indirect controls? Experiments have shown that reaction times are slower, and there is a higher variance in driving behavior like lane departure and maintaining speed 4.
Other disadvantages are the lack of haptic feedback when selecting an object and the display's placement, which is a trade-off between readability and reachability.
It is important to consider that there is no perfect solution for an interaction model of tertiary interactions that is easy to operate and not distracting. Carmakers should choose the 'least bad' solution in this case and design around its shortcomings.
When weighing the positives with the drawbacks of touch screens, they are the right solution for tertiary interactions in most cases if they are optimized for task completion time 5. The problem, though, is that currently, few of the interfaces are. This has much to do with the design choices of car companies.
Design Choices of Car Companies
Designing a touch interface is difficult, especially in the context of driving. As task completion time is the most significant advantage of touch screens, you would expect it to be one of the main acceptance criteria. Yet, many car companies don't seem to focus on that enough.
The perfect example of that is the latest trend of including secondary controls in the touch interface. For secondary interactions, the task completion time is already at a minimum with physical controls. On top of that, the physical controls require less visual attention. By moving those to a touch screen, both the task completion time and visual attention are compromised. It is not only annoying for end-users, but it is also dangerous.
Carmakers may do this because of decluttering and cost-saving. The aesthetics are important and may persuade customers to buy a car when they first see it. But good design is finding the right balance between ergonomics and aesthetics. When considering the dangers of driving, the first job of the designer should be to minimize distraction.
On top of that, the added benefit of prioritizing safety is that the controls will be more intuitive and easy to use. An interior will look super slick in the dealership if it has no physical buttons. Still, most buyers will find out very quickly after purchasing their car that it is annoying to have to divert visual attention to simply turn on the heater if before they could do it blindly. In moving the secondary controls to a touch interface, the balance is leaning too much towards aesthetics than ergonomics.
The second example of carmakers making suboptimal design decisions is the interface design itself, which is often needlessly complicated. They are filled with features that make you wonder why you would need them in a vehicle, like the possibility to check social media, order a pizza from the car, find movie times, or set custom wallpaper.
To carmakers, offering a lot of features equals customer value. But as many tech companies have shown, customer value is actually created by ensuring users achieve their goals. Having too many features stands in the way of that, and research confirms that. Year after year, infotainment systems are the biggest frustration in new car ownership, and the majority of problems are design-related 6. It may explain the popularity of Apple CarPlay and Android Auto. These systems are optimized for task completion time and restrict access to certain features and apps that are deemed too dangerous. As a result, they are less distracting than native infotainment systems 7.
Customers want the latest technology and apps to be available in their car. Designing an infotainment system in such a way that it is not distracting is impossible. In theory, touch screens are a valid technology to facilitate these interactions. However, car companies should be minimizing the risks of distraction. Today, there are significant steps to be made to get to that point. But there are reasons to be optimistic about the future.
Where Do We Go From Here?
The interior of the car is always transforming, and so are touch screens. There is a lot to be optimistic about. Lately, the hardware powering the infotainment systems has seen significant improvements, leading to better screens and faster interfaces. There will be more innovations like haptic feedback and new input types like gestures and better voice interaction in the next years. These will help to mitigate some of the disadvantages of touch screens.
Most carmakers are also getting serious about over-the-air updates, which will allow more iterations on the interface design to weed out usability issues. And with the increased importance of these interfaces, design teams in car companies are growing and gaining more experience.
In the end, it will be vital that they tip the balance more towards usability than aesthetics. But once they optimize their interfaces, and when combined with physical controls and other modalities, touch screens in cars will be a great solution.