  People park their vehicle depending on interior and exterior contexts. They
do it naturally, even unconsciously. For instance, with a baby seat on the
rear, the driver might leave more space on one side to be able to get the baby
out easily; or when grocery shopping, s/he may position the vehicle to remain
the trunk accessible. Autonomous vehicles are becoming technically effective at
driving from A to B and parking in a proper spot, with a default way. However,
in order to satisfy users' expectations and to become trustworthy, they will
also need to park or make a temporary stop, appropriate to the given situation.
In addition, users want to understand better the capabilities of their driving
assistance features, such as automated parking systems. A voice-based interface
can help with this and even ease the adoption of these features. Therefore, we
developed a voice-based in-car assistant (Park4U Mate), that is aware of
interior and exterior contexts (thanks to a variety of sensors), and that is
able to park autonomously in a smart way (with a constraints minimization
strategy). The solution was demonstrated to thirty-five users in test-drives
and their feedback was collected on the system's decision-making capability as
well as on the human-machine-interaction. The results show that: (1) the
proposed optimization algorithm is efficient at deciding the best parking
strategy; hence, autonomous vehicles can adopt it; (2) a voice-based digital
assistant for autonomous parking is perceived as a clear and effective
interaction method. However, the interaction speed remained the most important
criterion for users. In addition, they clearly wish not to be limited on only
voice-interaction, to use the automated parking function and rather appreciate
a multi-modal interaction.
