Interaction between humans and autonomous systems: Human facing
explanatory interface for an urban autonomous passenger ferry
Authors: Petermann Felix-marcel , Andreas Alsos Ole , Papachristou Eleftherios 
Published: February 2023

Problem statement During a public trial, over 150 passengers were
interviewed about their thoughts and experiences using an autonomous ferry,
among over 1500 passengers taking a trip on the world's first autonomous
urban passenger ferry in Trondheim. One of the main issues expressed by
passengers was a lack of information about the state of the unmanned ferry
service. A safety attendant was aboard for the three-week public testing to
take over control in the unlikely case of a hazardous event. Observations of
passengers revealed a desire for information regarding the functionality of
the ferry, the current state of the boat, and the progress of the current
journey. Passengers interviewed stated that, especially if no safety
personnel are on board, the demand for information is higher because no one
can be queried. The absence of information increased the sense of
insecurity. Since the space aboard the autonomous passenger ferry is
limited, the used option cannot be too spacious; nonetheless, the
information must be easily available to users. Research Question What
information do passengers require on a self-driving urban passenger ferry?
Does the type of information displayed affect passengers' perceptions of
safety? Method Two 10-inch high-luminance (1000 nits) screens have been
installed on the mast of the autonomous passenger ferry, allowing the user
to see information on both sides when embarking, disembarking, and
traveling. Two distinct information screen concepts have been visualized for
use in a semi-structured interview. First, the passengers were asked what
they could see on each of the concepts and what information they thought
would be most useful. They should also explain how the information they view
influences their sense of safety and trust. In an AB-test, passengers were
asked to select a preferred concept for the information screen and describe
why they chose that concept in detail. One of the concepts (A) was
straightforward and depicted the journey's progress as a linear bar.
Furthermore, the traveler could observe the ferry's status with a large
illustration, along with the status in one word and a brief description. The
second concept (B) should attract those passengers who are interested in
details and technical elements. Concept B contained an environment map with
the ferry's intended path and present position and heading, details for each
single thruster, the speed in kn, system health status, battery levels,
compass, object detection, and the ferry's current operation status. All
used and previously stated characteristics on both presented screens have
been used in a semi-open card sort to determine which information is most
valuable to the passengers. The passengers were instructed to prioritize the
offered information and fill in blank cards with missing information. Each
of the placed cards was awarded points based on their location in the
assortation; the further left the things were placed, the more points were
awarded; the further right, the fewer points were awarded. Results 15 of the
1500 passengers who participated in the public trial of the urban autonomous
passenger ferry were specifically asked about their preference for data
visualization and the demand for information on such a ferry. The majority
of the passengers (n = 12) indicated that they would prefer the simpler
version of the information concept (A), whereas the remainder of the
interviewed passengers would prefer the more technical interface because
they are more concerned with the ferry's functionality and the reliability
of the components. All of the users stated that they would feel less safe if
there was no safety attendant or information screens on board. The cart sort
analysis reveals that the more technical components have been ranked as less
relevant, with the ferry's state, system health, and continuous travel
progress being more important than detected objects, thruster details,
LiDAR, and radar visualization. Conclusion Both the interview data and the
card sort revealed that passengers on autonomous passenger ferries have a
higher demand for straightforward and immediately available information. If
they cannot obtain it from a human safety attendant on board, they require
additional information that is not overly technical in order to maintain a
high degree of safety perception.