We describe a study on the interaction design of in-car
navigation systems. It focused on a commercial
product. Critical incident analysis was performed
based on natural use of the system by a usability
analyst. A cognitive walkthrough was then performed
based on actual scenarios from the natural use. This
is a non-classic application of cognitive walkthrough.
It allowed anecdotal critical incidents to be
theoretically grounded. We draw conclusions about
the interaction design of car navigation systems
