  We propose that safe, beautiful, fulfilling vehicle HMI design must start
from a rigorous consideration of minimalist design. Modern vehicles are
changing from mechanical machines to mobile computing devices, similar to the
change from landline phones to smartphones. We propose the approach of
"designing toward minimalism", where we ask "why?" rather than "why not?" in
choosing what information to display to the driver. We demonstrate this
approach on an HMI case study of displaying vehicle speed. We first show that
vehicle speed is what 87.6% of people ask for. We then show, through an online
study with 1,038 subjects and 22,950 videos, that humans can estimate
ego-vehicle speed very well, especially at lower speeds. Thus, despite
believing that we need this information, we may not. In this way, we
demonstrate a systematic approach of questioning the fundamental assumptions of
what information is essential for vehicle HMI.
