Hey there and welcome to the presentation of our paper "Stop or Go? Let me Know!
A Field Study on Visual External Communication for Automated Shuttles".
My name is Alexander Mirnig and as you can see, there are quite a few authors on this one,
as this was a joint collaboration between two national Austrian flagship projects,
the first being Digibus Austria and the second one auto.bus Seestadt. Now let us get right into it:
This is about external communication for automated vehicles - why do we do that? Well, you might have
heard by now that one of the distinguishing features of automated vehicles, at least on
the higher automation levels, is that there will no longer be a human behind the wheel or at least
an actively involved one. And now the question is: What does this mean for the communication?
When we communicate between humans, what we do is we have something called 'eye contact'.
And what does that do? It primarily establishes a communication channel between us; it makes sure
that whoever I am having eye contact with I am communicating with them and not with
someone else with whom I have not. So it helps with clarity in the communication. Now replace
one of the humans with an automated vehicle and the communication might not be as clear anymore.
And this is the reason why you then see things like this, which are attempts to bring that
element back into the communication, to kind of give the eye contact back into the communication
between vehicle and human, whether or not there is a human behind the wheel or a human
pedestrian or anywhere else. And now the question we asked ourselves - and would like to pose - is:
How important is eye contact really? Well, it is very important in one kind of situation,
that is the 'deadlock situation'. Now what is a deadlock? Imagine the following: You are having
an intersection and there is one vehicle waiting at the intersection and then there is also another
vehicle waiting at the intersection and both of these want to enter the intersection but
since both of them are at a standstill, one of them has to drive first. Now the question is:
Which one of them will drive first? If they cannot come to a decision on this, then neither or both
might drive at the same time and none of this is satisfactory, hence it being called a 'deadlock'.
And this is typically resolved via gestures and eye contact: in a regular traffic situation,
one tells the other to please go ahead and drive, the other vehicle drives, and the
situation is resolved. So here, eye contact plays a very important role. But let us look
at some other situations. What if, for instance, you have the following: A vehicle is approaching
the intersection and another vehicle is also approaching the intersection and both of their
trajectories could perceivably cross but they are still quite a ways away from the intersection.
What decides here on what is going to happen? Or take another similar situation: The vehicle is,
once again, approaching the intersection from quite a distance away and there is a vehicle
already waiting at the intersection. Here, the question is: Is the vehicle going to depart or
is it going to stay there? And again: Will the trajectories cross or not and the question is,
once again: What decides on whether or not this situation is resolved or not - is it eye contact?
To further that question, let me show you something. This is what it can look like
if you're interacting in such a situation with an automated shuttle: You are approaching an
intersection and the shuttle slowly departs. There is no human in there with whom you could have eye
contact. The question is: Would it change anything if there was? Now take this situation right here:
You are passing an intersection and a shuttle is approaching and it might or it might not
stop (in this case it stops) and, once again, the question is: What was the deciding factor here?
These deciding factors are not so much the eye contact but more the vehicle's position,
the estimated vehicle trajectory, and - a derivative from this - the assumed intention
of acceleration or deceleration; and this is what we like to call 'driving initiative'
and it seems to us that, while eye contact is far from unimportant, to be the deciding
factor in a great many of potentially very critical situations. And as you have also seen
in the videos, these shuttles, at least the way they currently are, are driving in a very specific
kind of way, so it is difficult to estimate the intention of acceleration or deceleration based on
what you know from other human drivers, because they have low top speeds, they stop very abruptly
and even if they wanted to, they can only accelerate so fast. So it is not a trivial matter
and this is why we set ourselves a goal to help with that: to communicate the driving
initiative of such automated shuttles and as for the way to do so we chose an external
light band HMI (eHMI). We did this in relation to three factors: We wanted to know,
if such eHMIs would be perceived by other road users - are they visible enough? If they are
visible, do they actually help? Are they useful? Do they support the resolution of such situations?
And: How safe are they? Can they help us avoid unsafe situations
and hopefully they don't make the situations unsafer than they already are.
That is what we set out to do and we did this via two comparably simple implementations. The
first one was a simple traffic light metaphor (red-green) implementation. All we did was
use the traffic light metaphor in the same way it is used in an actual traffic light,
so when the shuttle accelerates away from a standstill it, displays red meaning that
"Other vehicles, please stop - I'm going now," and the inverse is true for green where the
shuttle decelerates and displays green to show "I'm stopping now, you can go." Then, we made
a separate condition - the animation condition - where we communicated the same contents
but this time via an animation. Here, the light on the band HMI
goes outwards when the vehicle accelerates to communicate the acceleration behavior,
to anticipate it before it happens. It contracts when the vehicle decelerates.
And that is essentially what it was: to simply communicate the driving initiative, to anticipate
the driving initiative, before it happens and make it a little bit easier for the drivers
of other vehicles to adjust themselves based on what the shuttle is doing or planning to do.
And this is what it looked like on the actual vehicles: On the left you can see
the Navya Arma and on the right the EasyMile EZ10. Both of these photos were taken under different
lighting conditions so that you can see the actual led strips on the right as it was being installed
and the left one as it is being run on full power - but they looked the same
on both of these shuttles. Now you might be asking: Why were these on two shuttles? And
the reason for that is that we had two test environments, based on the two projects.
One was in a small rural town called Koppl bei Salzburg and another one in the Seestadt
Aspern. What we did here is we had these shuttles circulate and at every intersection - these are
the ones that you can see here marked with numbers - we had the vehicle display the respective cues
via the light band HMIs in the two conditions (or nothing in the control condition) and
we had the shuttle go several rounds across several days and then took the data from there
to see how well they worked (or didn't). And the way we did this was via an observation approach:
we defined a number of metrics regarding the three factors visibility, usefulness, and safety;
and then logged the behavior of both the traffic participants and the shuttle's behavior based on
what the traffic participants did or did not do and then had a success and a failure condition
for each of these scenarios. For instance, if the shuttle would try to depart and then
would have to stop again because it hadn't been certain to the other road users that the shuttle
wanted to depart, then that was a failure condition. If, on the other hand, the shuttle
had precedence and could depart without incident, then that would be logged as a success condition.
Now, there is only so much you can talk about in 10 minutes so if you want to have more details
on how the study was set up, how the data collection worked, and what we found out,
please do check out the paper. What i want to do in the following is to simply give you
a few of the of the things that stood out in terms of discussion points. One of the things,
obviously, that we wanted to find out is: Are the light band eHMIs useful? Do they improve
performance? And we found the thing that you would like to find out in this situation that yes, they
were useful. We had improved performance across the board when the light band eHMIs were engaged
in comparison to the control condition. There was one or two isolated incidents where we actually
had a slightly worse performance but it was always within a small margin and not significant.
But, in relation to this, the success rates in the control condition were already pretty high. This
means that the improvement potential by the eHMIs was rather limited. This is good news in a way,
as it means that these shuttles are not driving disasters waiting to happen, so
even with no additional visualizations it worked rather well. But there were still improvements
to be had with an external light band HMI. But what we also found is that the the differences
between the red-green and the animation conditions were almost negligible. It seemed like you could
get an improvement in performance simply by having something there that is not a standard
indicator and which captures the attention of the road environment and then they will
pay attention to what is happening around them and adjust their behavior accordingly.
It did not seem to matter as much whether or not we used the traffic light metaphor or some kind
of other metaphor, as long as at least something was there. And so this is interesting because it
seemed as if the specific animation visualization mode does not matter as much as we thought.
Anyway, that is already more than what I can put into 10 minutes,
so unfortunately, I have to leave it with that but to wrap it all up: We did find
driving initiative to be a relevant factor, light band eHMIs to be suitable
to address these (factors) but we also found that the improvement potential was limited and that
what happened on the eHMI seemed not so important as the eHMI to simply be there.
So the thought I would like to leave you with is that we should maybe revisit this a few more times
look at what is actually needed - which contents do we need to communicate and what do we actually
need to put on the vehicles? And how much is too much? If we don't want to end up with this,
then that is maybe a question we should ask ourselves. We will also try to ask ourselves this
in future research efforts and this is the thought i want to leave you with. I thank