Do touchscreens in cars really not work?
After all, multi-modal HMI concepts - basing on a touch-screen-first approach - are the only guarantee for success.
I recently enjoyed Jacky Li's (from Connected Lab) relevant summary of what is wrong with touchscreen-only interaction in cars. Read article here.
Having tested more than 50 car interfaces with several hundred participants, I would say that the key to good in-car usability is not focusing on one input methodology but to offer true multi-modality. Users might struggle with touchscreen input while driving but it is still superior in speed to jog-dial input while standing. Also, while offline voice control is constantly improving (e.g. as in the 2018 Mercedes A-class), it often still does not provide the same accuracy as manual data input (especially for setting navigation destination). In addition, many participants in our studies are still not comfortable with voice input or state that they would not want to use it when riding with (potentially noisy) passengers. I would add two more aspects to the discussion of touchscreen usability in cars:
The position of the touch screen and the physical distance to the driver is essential
In many (especially top tier) cars, the touch screen is located at a great distance from the driver (the Tesla S is a good example for this), which makes it very difficult for the driver to reach and interact with it while driving. In a worst-case scenario, each interaction with the touchscreen requires a shift in position for the driver, which makes it more difficult for her to pay attention to traffic. I personally have tested many cars in the low tiers which only relied on touchscreen interaction and where I felt much safer while observing a driving participant - this was mostly due to the proximity of the display to the participant which they could reach without having to fully extend their arm or changing their posture.
The information architecture should be adapted to touchscreen mindset
In several cars we have tested, manufacturers have made the shift from purely jog-dial / hard-button interaction to also include touch interaction. The information architecture of the system, however, was still routed in a jog-dial mindset. An example for this is the first BMW 7 with touch screen. It was very hard for users to interact with the touchscreen system efficiently, as they still had to traverse the navigation paths which were clearly optimized for a different kind of interaction. However, as Jacky also points out, users tend to be distracted by the presence of touchscreens in general - a problem that could be addressed by implementing cluster and head up displays which display all relevant information, removing the need to constantly look at the central display.