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Testing unfinished automated driving technology on public roads:
Results from interviews with participants of Tesla’s Full-Self
Driving (FSD) Beta
Sina Nordhoff a, John D. Lee b, Simeon C. Calvert a, Siri Berge a, Marjan Hagenzieker a,
Riender Happee c
a Department Transport & Planning, Delft University of Technology, The Netherlands
b Department of Industrial and Systems Engineering, University of Wisconsin-Madison,
United Stated States of America
c Department Cognitive Robotics, Delft University of Technology,
The Netherlands
ABSTRACT
Tesla’s Full Self-Driving Beta (FSD) program introduces technology that extends the operational design
domain of standard Autopilot from highways to urban roads. This research conducted 103 semi-structured
interviews with users of Tesla’s FSD Beta and standard Autopilot to evaluate the impact on user behavior
and perception. It was found that drivers became complacent over time with Autopilot engaged, failing to
monitor the system, and engaging in safety-critical behaviors such as hands-free driving enabled by weights
placed on the steering wheel, mind wandering, or sleeping behind the wheel. Drivers’ movement of eyes,
hands, and feet became more relaxed with experience with Autopilot engaged. FSD Beta required constant
supervision as unfinished technology, which increased driver stress, and mental and physical workload as
drivers had to be constantly prepared for unsafe system behavior (doing the wrong thing at the worst time).
The hands-on wheel check was not considered as being necessarily effective in driver monitoring and
guaranteeing safe use. Drivers adapt to automation over time, engaging in potentially dangerous behaviors.
Some behavior seems to be a knowing violation of intended use (e.g., weighting the steering wheel), and
other behavior reflects a misunderstanding or lack of experience (e.g., using Autopilot on roads not
designed for). As unfinished Beta technology, FSD Beta can introduce new forms of stress and can be
inherently unsafe. We recommend future research to investigate to what extent these behavioral changes
affect accident risk, and can be alleviated through driver state monitoring and assistance.
Keywords: Full Self-Driving (FSD) Beta, automated driving, traffic safety, human factors, mind-off driving
1. Introduction
Tesla’s Autopilot is amongst the most capable and discussed partially automated driving systems currently
available to drivers in production vehicles throughout the world. In October 2020, Tesla launched its Full
Self-Driving (FSD) Beta program, which is a SAE Level 2 partially automated driving system extending
the operational design domain (ODD) of standard Autopilot – the highway – enabling the car to drive in
automated mode on non-highway roads under the constant supervision of human drivers. Currently, around
160,000 pre-selected owners and drivers have been given access to FSD Beta (Korosec, 2021; Lambert,
2022a, 2022b; Quick, 2022). FSD Beta has been controversially described as an “experiment on public
roads” (Petrova, 2022) given unsafe vehicle behavior (Lambert, 2020), which prompted the California
Department for Motor Vehicles to re-assess the FSD Beta trial (Lambert, 2022a).
The introduction of Connected Intelligent Transport Systems (C–ITS) and new in-car technology is
associated with a direct in-vehicle modification of the driving task, indirect modification of user behavior,
modification of exposure and route choice (Kulmala, 2010).
The direct modification of the in-vehicle driving task, which represents the short-term, intended,
engineering effects as a direct consequence of system use can relate to driver state changes (i.e., attention,
situational awareness, workload, stress, drowsiness), and decisions about action / performance changes (i.e.,
driving, system handling, error) (Kulmala, 2010; Martens & Jenssen, 2012). Theoretical assumptions and
empirical evidence about the effect of partially automated driving on drivers’ situational awareness and
workload are mixed, with some studies expecting a decrease in situational awareness (Boelhouwer, Van
Dijk, & Martens, 2019; White et al., 2019), and others reporting an increase in situational awareness (Mica
R Endsley, 2017). A meta-analysis by De Winter, Happee, Martens, and Stanton (2014) showed that
Adaptive Cruise Control (ACC) and Highly Automated Driving (HAD) (corresponding with conditionally
automated driving) could both increase and decrease driver’s situational awareness. The authors further
reveal that HAD resulted in a substantial decrease of workload, while ACC reduced drivers’ workload by
only a small amount. Metz et al. (2021) have revealed an increase in driver fatigue during the drive with
automated driving functions.
The indirect modification of user behavior pertain to the unintended longer-term positive and negative
behavioral changes of human drivers adapting to the system (Lee, 2008; Martens & Jenssen, 2012; Sagberg,
Fosser, & Sætermo, 1997). These can offset or negate some of the intended benefits (Martens & Jenssen,
2012; Robertson, Meister, Vanlaar, & Mainegra Hing, 2017). Human Factors researchers have long pointed
to the ‘ironies of automation’ (Bainbridge, 1983), changing the role of the human driver from manual to
supervisory control, and creating so-called ‘out of the loop’ issues (Saffarian, De Winter, & Happee, 2012).
Unintended effects can pertain to changes in driver state, performance (see Section 2.1), and attitudes, such
as trust, overreliance, acceptance and rejection (Martens & Jenssen, 2012). Mis-calibrated trust can take the
form of overtrust (trust is higher than what is required by the system) and promote misuse (i.e., overreliance
on automation), whereas undertrust can promote disuse of automation (i.e., underutilization of automation)
(Lee, 2008; Parasuraman & Riley, 1997). A common example of misuse is complacency, which occurs
when drivers fail to monitor the system (Banks, Eriksson, O'Donoghue, & Stanton, 2018; Cotter, Atchley,
Banz, & Tenhundfeld, 2021; Lee, 2008). Other unintended reported behavioral effects were mode confusion
(Banks et al., 2018; Mica R Endsley, 2017; Wilson, Yang, Roady, Kuo, & Lenné, 2020), testing the limits
of the operational design domain (Banks et al., 2018), using Autopilot in operational design domains for
which it was not intended (Kim, Song, & Doerzaph, 2021), driver distraction, drowsiness, and the difficulty
of handling unanticipated automation failures (Endsley, 2017), an inadequate mental model of the
capabilities of the automation, and skill degradation (i.e., loss of manual control skills due to automation)
(Saffarian et al., 2012). Other studies provided evidence for little differences between the self-reported
secondary task engagement during manual and partially automated driving (Nordhoff, Stapel, He, Gentner,
& Happee, 2021; Shutko, Osafo-Yeboah, Rockwell, & Palmer, 2018). Evidence as to whether secondary
task engagement deteriorates drivers’ take-over performance is inconclusive (Lin, Liu, Ma, Zhang, &
Zhang, 2019).
The modification of exposure and route choice covers the changes in the amount of travelling (i.e., number
of trips, length of trips) and mode choice (Kulmala, 2010). Scientific evidence on the expected changes in
the amount of travelling – increase, decrease, or no change in the vehicle miles travelled – associated with
the use of automated cars is ambiguous. Automated vehicles are expected to increase the productive use of
travel time, which might encourage people to accept longer commutes (Singleton, 2019). Studies have
revealed an expected increase in the vehicle miles travelled (Gurumurthy & Kockelman, 2020; Harb, Xiao,
Circella, Mokhtarian, & Walker, 2018; Hardman, Lee, & Tal, 2019; Lehtonen et al., 2022; Perrine,
Kockelman, & Huang, 2020; Schoettle & Sivak, 2015). Other studies have found no increase in the vehicle
miles travelled (Zmud, Sener, & Wagner, 2016), and others provided evidence for both an increase and
decrease in the vehicle miles travelled due to using automated vehicles (Childress, Nichols, Charlton, &
Coe, 2015; Wadud, MacKenzie, & Leiby, 2016).
1.1. The present study
It is assumed that automated cars will improve traffic safety, eliminating human error (Tafidis, Farah, Brijs,
& Pirdavani, 2022; Ye & Yamamoto, 2019). These assumptions tend to remain speculative and untested,
ignoring the emergence of new types of unintended safety risks, which may offset the expected safety
benefits (Casner & Hutchins, 2019; Malin, Silla, Mesimäki, Innamaa, & Peltola, 2022; McWilliams &
Ward, 2021; Tafidis et al., 2022). Except for social media content (e.g., anecdotes, YouTube videos)
(Reddit, 2022a), little is known about the unintended and intended changes of the user behavior with FSD
Beta engaged, and in comparison to Autopilot. An analysis of the intended and unintended changes on the
users of these systems and new types of safety risks that may emerge with the introduction of these systems
will provide valuable information for manufacturers and policy-makers on the safe introduction of
automated vehicles on public roads.
The main objective of the present study is to explore to what extent the use of FSD Beta and Autopilot
contribute to:
- Direct in-vehicle modifications of the driving task (i.e., direct, short-term reaction of driver to
introduction of the system, with effects being a direct consequence of system use, appearing
directly after system use; effects can be both intended or unintended);
- Indirect modification of user behavior (i.e., long-term behavioral adaptation of driver in unknown
ways, with effects not appearing immediately after system use);
- Modification of road exposure (changes in the amount of travelling, i.e., number of trips, trip
length);
- Modification of route choice (i.e., changes in modal choice) (Kulmala, 2010).
2. Method
2.1. Recruitment & procedure
Semi-structured interviews were conducted with participants of Tesla’s FSD Beta program, and users of
standard Autopilot. The study was approved by the Human Research Ethics Committee of Delft University
of Technology in the Netherlands.
Participants of the FSD Beta program were selected by Tesla, providing early access to owners (e.g.,
presidents of Tesla Owner clubs), and to drivers with a high safety score (Korosec, 2021; Lambert, 2022a,
2022b). They received the following instructions from Tesla via email prior to use of FSD Beta:
Full Self-Driving is in limited early access Beta and must be used with additional caution. It
may do the wrong thing at the worst time, so you must always keep your hands on the wheel
and pay extra attention to the road. Do not become complacent. When Full Self-Driving Beta
is enabled, your vehicle will make lane changes off highway, select forks to follow your
navigation route, navigate around other vehicles and objects, and make left and right turns.
Use Full Self-Driving Beta only if you will pay constant attention to the road, and be prepared
to act immediately, especially around blind corners, crossing intersections, and in narrow
driving situations. Every driver is responsible for remaining alert and active when using
Autopilot and must be prepared to take action at any time.
As part of receiving FSD Beta, your vehicle will collect and share VIN-associated vehicle
driving data with Tesla to confirm your continued eligibility for FSD Beta feature. If you wish
to be removed from the limited early access FSD Beta please email xxx.
For this study, respondents using FSD Beta were targeted via specialized online communities and forums
(i.e., Discord, Facebook, Twitter, Reddit, Tesla Motors Club). As FSD Beta was only available to drivers
of North America and Canada by the time the study was conducted, the focus of the recruiting targeted but
was not limited to these geographic locations. The ownership of a Tesla was subjectively using self-reported
data pertaining to the model and frequency of use of the Tesla.
Respondents were interviewed on-line using Zoom recording both sound and vision. The interview protocol
was created on Qualtrics (www.Qualtrics.com). This questionnaire consisted of open-ended and closed-
ended questions. Qualtrics used several technologies (e.g., bot detection, security scan monitor, and index
preventing) to enhance data quality. At the start of the Zoom interview, respondents were sent a link to the
questionnaire via the chat function of Zoom so that respondents directly saw the questions in front of them,
being able to independently move to the next question once they answered a question. The main role of the
researcher was to listen as respondents completed the questionnaire to reduce the risk of influencing
respondents during the interview. As the questions were standardized and logically followed each other,
the intervention of the researcher was limited.
The interview protocol was divided into two main parts. At the start of the interview, respondents were
asked to provide their informed consent to participate in the study. The first part consisted of mostly open-
ended questions, while the second part consisted mostly of closed-ended questions pertaining to
respondents’ socio-demographic profile and travel behavior (e.g., age, gender, highest level of education,
frequency of use of Autopilot and FSD Beta) and general attitudes towards traffic safety.
Subjected to the analysis of the present paper were the questions Q1, Q4, Q25–Q27, Q31–Q35. With
question Q1, respondents were asked to indicate whether they have the Full Self-Driving Beta (FSD Beta)
feature. With Q4, respondents were asked to describe their general experiences with using Autopilot and
FSD Beta, and the benefits and risk associated with using it. Questions Q25–Q27, Q31–Q34 asked
respondents to indicate their placement of hands on the steering wheel, eyes on the road, and feet on the
pedals when Autopilot and FSD Beta are active, and whether they typically stay prepared to take corrective
actions at all times. Respondents were asked to answer every question specifically for Autopilot and FSD
Beta, respectively, in order to reflect on the differences between the systems per question if applicable.
Table 1 in the appendix presents an overview of the questions asked in the first part of the interview. The
questions that were not subjected to the analysis of this study will be processed in following studies as it is
beyond the scope of the present study to analyze the responses obtained for these questions in sufficient
detail.
2.2. Data analysis
Following the procedure adopted in previous interview studies (Doubek, Salzmann, & De Winter, 2021;
Nordhoff, De Winter, Payre, van Arem, & Happee, 2019), the data analysis was performed in four steps:
1. First, the interviews were transcribed verbatim.
2. In the second step, the main categories were developed deductively using the three dimensions –
direct in-vehicle modification of the driving task, indirect modification of user behavior, and
modification of exposure and route choice – of the safety assessment framework by Kulmala
(2010). Next, the sub-categories were developed following principles of inductive category
development by Mayring (2000).
3. In the third step, the number of sub-categories mentioned by respondents was counted. When a
sub-category was mentioned more than once per respondent, the number of mentions equaled a
frequency of 1. Subcategories had to be mentioned by at least 5 respondents to be eligible for the
formation of a sub-category.
4. In the fourth step of the analysis, a maximum number of five illustrative quotes were selected to
portray the meaning of each sub-category. Multiple mentions of a sub-category per respondent were
not discarded but merged with the other mentions of the subcategory by the respondent. Therefore,
some of the quotes represent clusters of sentences mentioned by the same respondents at different
points during the interview. Filler words and repetitions (e.g., you know”, “like”, “uhhm”) were
excluded from the quotes.
3. Results
103 semi-structured interviews were conducted between February and June 2022. On average, an interview
lasted 01:18:05 hours. Respondents were on average 42.72 years old with a standard deviation of 14.14
years. 91% were male, and 9% were female. 52% had a Bachelor or Master degree, 27% a college degree,
13% a high school diploma, and 8% a PhD degree. The three most common residential locations were
California (20%), Colorado (8%), and Florida (7%). Respondents reported to be engineers (30%), managers
(8%), or retired (7%). 82% of respondents indicated to have access to FSD Beta and standard Autopilot,
while 18% only had access to Autopilot. Respondents’ average use of Autopilot and FSD Beta was 26.8
and 8.14 months, respectively. Respondents’ frequency of use of Autopilot and FSD Beta was 4.11 and
4.50, respectively (measured on a scale from 1 = Less than monthly, 2 = Less than weekly but more than
once a month, 3 = 1–2 times a week, 4 = 3–4 times a week to 5 = At least five times a week). Five interviews
were conducted in German (R04, R09, R15, R47, R89) as the respondents were German native speakers.
The results of the data analysis are divided into three main categories and fifteen sub-categories. The three
main categories are the indirect modification of user behavior (10), direct in-vehicle modification of the
driving task (3), and modification of exposure and route choice (2). Figure 1 presents an overview of these
main categories and sub-categories. The three sub-categories mentioned most often pertained to the
decrease in workload with Autopilot engaged, an increase in one-hand driving, and using Autopilot in
ODD’s not designed for, with 63%, 53%, and 43% of respondents mentioning these sub-categories,
respectively.
Figure 1. Visual representation of results of data analysis, main categories and sub-categories extracted
from the interview data
Table 2 presents an overview of the main categories and sub-categories extracted from the data analysis,
their observed effect, and meaning of the subcategories. Observed effects (column 3 in Table 1) were highly
consistent over participants in most cases (+ or -), while unclear results were found in other cases (NA). The
results are discussed in the subsequent sections.
Table 2. Results of data analysis; i.e., main category, sub-category, observed effect (negative = -, positive
= +, NA = not available), meaning of sub-category, number (n) of respondents mentioning sub-category
Main
category
Sub-category
Observed
effect
Meaning
n
Indirect modification
of user behavior
Aggressive driving
-
Decrease of driver aggression towards other drivers on the
road (including speeding and reckless driving) with
Autopilot overtaking driving in stressful and monotonous
situations and interacting with other road users
13
Dual role of driver and
passenger
NA
Dual role of human operator as driver and passenger
12
Overreliance
+
Overreliance on Autopilot due to expected safety benefits
when driver is distracted, impaired or during inclement
weather conditions (e.g., rain, night)
23
Using Autopilot in ODD’s not
designed for
NA
Using Autopilot in ODD’s for which it was not designed
(i.e., non-highway roads, roundabouts, curves, hills, poor
visibility conditions) (Tesla, 2022a) due to lack of
knowledge, experimental attitude to test the system,
overtrust, or apparent system competence
44
Complacency (eyes-off road
driving)
+
Increase in complacency (eyes-off road driving) with
Autopilot engaged due to overtrust in system capability
proven over time, contributing to failures to monitor
automated driving system, and engaging in secondary
tasks
42
One-hand driving
+
Increase in one-hand driving due to overtrust in system
capability proven over time and the need to satisfy the
steering wheel torque sensor
55
Hands-free driving
+
Increase in hands-free driving beyond the technical
system specifications (i.e., nagging), enabled by e.g.,
weighting the steering wheel, or placing knees on steering
wheel, resulting in complacency and secondary task
engagement
22
Mind-off and fatigued driving
+
Increase in mind-off and fatigued driving with Autopilot
engaged (i.e., mind wandering, sleeping) due to overtrust
in system capability proven over time
12
Ability of taking over control
NA
Improved ability of taking over control with FSD Beta
engaged given status as technology under development
and constant need for supervision in comparison with
impaired ability of taking over control with Autopilot
engaged, with more relaxed placement of eyes, hands, and
feet in familiar, trustworthy situations
31
Skill degradation
+
Loss of skills and increase of discomfort driving
traditional, non-automated car
17
Direct in-vehicle
modification of the
driving task
Situational awareness
+
Increase in situational awareness with Autopilot engaged
(i.e., perception of events in vehicle’s environment) in
terms of ability to monitor vehicle surroundings
42
Workload
-
Decrease in mental and physical workload with Autopilot
engaged due to lateral and longitudinal control of driving
task, and increases in situational awareness, resulting in
reduction of driver fatigue, making driving (more)
relaxing, and easier than manual driving
65
+
Increase in workload with FSD Beta engaged given status
as technology under development and high
disengagement rate, making driving not relaxing
21
Stress
-
Decrease in stress with Autopilot engaged due to lateral
and longitudinal control of driving task, reduction in
workload, and aggressive driving (including speeding and
reckless driving)
32
+
Increase in stress while driving with FSD Beta engaged
given status as technology under development and
constant need for supervision
15
Modification of
travelling
Exposure
+
Using Autopilot on long-distance road trips due to
efficiency and safety benefits and positive effects
pertaining to driver state
43
Route choice
NA
Changes in route choice with FSD Beta engaged given its
status as technology under development and motivation
to contribute to the development of system and fully
automated driving
8
3.1. Indirect modification of user behavior
3.1.1. Aggressive driving
This sub-theme covered the reduction in aggressive driving towards other drivers on the road, including
speeding and reckless driving when Autopilot is engaged, reducing the stress of driving, and making driving
more relaxing.
“It removes a lot of the stress of driving. I just put it into Autopilot and if the
cars are slowing down, speeding up, I don’t really care. I just sit there and
watch the road. Whereas if I’m driving, I’m constantly trying to move around
cars and hitting the brakes and it’s much more stressful. So, it makes driving
a lot more relaxing.” (R046)
“I used to speed, and I used to drive pretty dangerously. With Autopilot, I just
don’t worry about it anymore. I’ll get to my destination when I get there, and
I just let the car handle the drive. So it made me a safer driver. Autopilot just
calmed me right the hell down. Just chill, driver. That’s what I am now.”
(R054)
“Another reason I really like using full self-driving is it is making me a better
driver. When I outsource my driving to the car, the chances of me getting a
speeding ticket go down by orders of magnitude. When there are other cars
on the road that are weaving in and out of lanes and trying to get ahead of
other drivers, I just don’t really care. The human nature aspect of driving, the
competitive nature, or the aggression that you might have towards another
driver or if you’ve had a stressful day, none of those things really matter
anymore.” (R065)
“I’m coming from a place where I have multiple speeding tickets. I was … I’m
a very aggressive driver. I have, reckless driving charges. Autopilot probably
just makes me a better driver because I just don’t care anymore about
speeding, about the aggression that other people are dishing out at me. It turns
me into a very meek driver, it takes away all my aggression, basically.”
(R074)
3.1.2. Dual role of operator being a driver and passenger
This sub-theme covers the changing role of drivers into passengers with Autopilot and FSD Beta engaged,
with respondents monitoring the operation of the system as passengers while still being required to take
over control and operate the car as drivers.
“I’ll be completely honest with you. When I first got it [Autopilot], I probably
wasn’t paying … I probably was a little bit over trusting maybe. I ended up
hitting road debris or something and then it kind of scared me and I was like
‘Oh, crap. I actually have to pay attention.’ So that first experience probably
jolted me back into to like ‘I’m not a passenger.’” (R006)
“I described the FSD as a 5-year-old learning to drive right and then inflicting
that on you as a passenger.” (R042)
“The benefit just in general is, it feels a lot more like being an observer.
Almost being in a car with a student driver or being in a car with a teenager
where you’re kind of just observing them, you’re not really doing anything for
them.” (R045)
“When going through high traffic scenarios, I just let it maintain the distance
between me and the car ahead of me and I just do my thing. I am a passenger
in the vehicle, and I just need to make sure I don’t miss my exit, or I don’t miss
my turn at that point.” (R054)
“I almost feel like I’m a passenger in the car, but it’s like better than being a
passenger because I’m still in control.” (R068)
3.1.3. Overreliance
This sub-theme covered respondents’ (over-)reliance on Autopilot due to the expected safety benefits in
situations in which drivers are distracted, impaired or during inclement weather conditions.
"If I’m tired or if I’m not paying enough attention, just knowing that it’s going
to be able to drive for me for a short amount of time is what it does best.
Especially on the highway, I know that I can just kind of not go to sleep or
anything, but I can relax and lean back and just give myself a mental break
for a few minutes and I know that the car is gonna handle everything without
any issues.” (R022)
“If I want to have that second set of eyes kind of patiently paying attention to
the road where I know that maybe I’ll be distracted by selecting music or on
a phone call or honestly, if I’ve had a few too many drinks, it really does come
in handy for that.” (R027)
“When I was driving home a week or two ago from Maryland, it was one of
those cases where you get on the highway and your next offramp is in 200
kilometers. You get into the groove; you’re listening to music. You’re not
paying attention. Suddenly, my car put its blinkers on and started to change
into the offramp and I’m like ‘What? What are you doing?’ I disengaged Full
Self-Driving thinking it was a problem, and then I looked at the map and I’m
like ‘Oh, this is my offramp.’ I would have missed my offramp if it wasn’t for
FSD.” (R044)
“There’s plenty drives where you are tired, at the end of the workday.
Sometimes as a driver, you’re not paying perfect attention, you’re not fully
energized, you’re tired, you’re distracted. It just feels like a safety thing too.”
(R070)
“I actually do feel safer on that on limited access highways at night when I’m
very tired because driving without such assist, I’m afraid of microsleep events
if I’m very tired or fatigued which is where you basically fall asleep for maybe
one or two seconds. Having a system there to back me up in those sort of
situations makes me feel significantly safer than driving a standard vehicle.
This came into effect two weeks ago for me.” (R090)
3.1.4. Using Autopilot in ODDs not designed for
This sub-theme covers using Autopilot in ODDs for which it was not designed, due to the apparent system
competence to operate in these situations, a lack of knowledge, (over-)trust, or curiosity to use it in these
situations.
“I used it from the start and then noticed very quickly that I can use Autopilot
also on roads other than freeways.” (R039)
“The first time I used Autopilot, I didn’t really realize what it was meant for.
It was meant for highway driving. I was using it on streets.” (R052)
“I was using Autopilot on city driving just for straight roads. There was one
instance where I was crossing an intersection and Autopilot just braked out of
nowhere and I was really confused and all of a sudden, a car in front of me
passed through at a high-speed flying by, when I had a green light.” (R075)
“Autopilot – that’s what traditionally was only on the freeway, but you could
use Autopilot in town, and I use it all the time. You’ve been in town even
though it didn’t work very good in town.” (R095)
3.1.5. Complacency (eyes-off road driving)
This sub-theme covers the risk of complacency associated with using Autopilot. Complacency implies the
failure to monitor the system due to consistently reliable system capability proven over time in simple,
trustworthy environments, lulling drivers into a false sense of safety. It can result in taking eyes off the road
and engaging in secondary activities.
“With Autopilot, I pretty much don’t pay that much attention anymore on
roads that I’m familiar with. If my boss or someone sends an email, I am more
comfortable, taking my eyes off the road for 15–20 seconds to reply. I look up
occasionally just to make sure there’s something on the road. Usually, I am
reading something, flipping through a presentation or emails, reading paper
materials or something on my phone or iPad. I’ve actually always done that
even without a Tesla. I used to read an entire Wall Street Journal on my phone
in a Honda Civic.” (R033)
“I have gone 44 miles without looking up on Autopilot. It’s all on freeway, but
I don’t even have to worry about it. So that part is great. So it’s not a difficult,
complicated drive, but I don’t worry at all about it.” (R042)
“This is an experience I have on Autopilot I’ve had a giant block of Styrofoam
in the road and of course, I wasn’t attentive. I’ve drove this road over so often.
We’re not paying attention. I talked with Molly about something, and I look
ahead and in front of me is that piece of Styrofoam. The car didn’t see it, and
we ran it over.” (R048)
“When Autopilot is active, I feel safe enough that I can take my eyes off the
road for a couple minutes and I generally will only do that if I can see really
far in front of me, I’m going straight and there’s no turns. Then I know it’s
safe to take my eyes off the road. I know you shouldn’t do that, but I’m doing
it in a controlled environment where I’ve had almost three years of experience
with Autopilot.” (R055)
“It’s kind of nice, especially in long trips. You set it and forget it pretty much
and the car just basically drives you. I mean, you still have to pay attention,
but it’s a lot easier.” (R058)
Respondents were more prone to monitor the road with FSD Beta, which required a higher level of
supervision than Autopilot for the reasons mentioned before.
“Talking about the Beta that I have for city driving, you need to be 150%
paying attention because the car is going to do something stupid. That thing
should not be released to the masses now. It really should not. I hope they
don’t.” (R001)
“FSD Beta. I can’t look away even for a half second. It just changed lanes on
its own.” (R007)
“I feel like if I didn’t intervene right there, that truck that was stopped at that
light would have gotten hit and that would have been a collision. That’s one
good example of FSD Beta why I need to stay active. I need to pretty much be
alert at all times right there to take over because it will do the wrong thing at
the wrong time.” (R048)
“Generally testing FSD Beta, I know that I’m using software that is not ready
for any random person in the world to use because it requires literally full
attention all the time. I’m driving at like 200% attention with FSD Beta. For
Autopilot, it’s like 80% of my normal attention while driving. There’s just not
much to pay attention to when it goes straight.” (R055)
3.1.6. One-hand driving
This sub-theme covers incidences of one-hand driving with Autopilot and FSD Beta engaged.
The position of respondents’ hands on the steering wheel when Autopilot and FSD Beta are active is shown
in the Figures 2 and 3. As shown by Figure 2, 48% of respondents reported to place their hands at the
bottom of the steering wheel when Autopilot is engaged, followed by the ‘3 to 9 o’clock’ position. 42% of
respondents reported to have their hands at the ‘3 to 9 o’clock’ position when FSD Beta is engaged,
followed by 32% of respondents placing their hands at the bottom of the wheel (Figure 3).
Figure 2. Placement of hands-on steering wheel with Autopilot engaged. Multiple responses were
allowed.
24%
21%
48%
6%
1
2
4
3
42%
22%
32%
5%
1
2
4
3
Figure 3. Placement of hands-on steering wheel with FSD Beta engaged. Multiple responses were
allowed.
Respondents mentioned that they engaged in one-hand driving with both systems engaged. One-hand
driving occurred because it is more comfortable, or necessary to satisfy the steering wheel torque sensor.
Respondents questioned the suitability of the torque-based steering wheel driver monitoring system, not
being necessarily effective in driver monitoring and guaranteeing safe use. It was mentioned that rather
than actively steering the vehicle, the hands were placed on the steering wheel mainly to satisfy the
steering wheel torque sensor because the weight of two hands placed on the steering wheel could result
in accidently disengaging the system.
“The hands-on feature is a very clumsy method in my opinion of ensuring
driver attention. I’d much rather be on the road with someone whose hands
are off the steering wheel, but they’re paying attention than someone who’s
hand is resting on the steering wheel, but they’re checking their email.
From a moral perspective, I think the hands-on feature is debatable,
whether it’s masks a moral necessity, or whether it’s just a legal
appeasement.” (R007)
“I keep a hand on the steering wheel at all times. Not both hands. I keep the
hand on just enough to satisfy the torquing requirement where there needs to
be weight on the system.” (R054)
“They could get off the steering wheel nag because actually you could apply
too much torque while you’re trying to make sure it knows you’re paying
attention and that takes it out of full self-driving Beta, and that could be a
shock if you aren’t ready for it. My hands are always on the steering wheel
but to make sure you have to keep the torque all the time it’s safety issue.”
(R062)
“I think probably still one-handed. If I’m using two hands, I’m just driving
myself usually. It feels kind of hard using two hands while using Autopilot
because the torque thing and you don’t wanna touch it enough to take it out
of it.” (R070)
Figure 4 provides an overview of additional positions of hands and feet when Autopilot and FSD Beta
are active.
Figure 4. Additional positions of hands and feet when Autopilot and FSD Beta are engaged; images 6
and 14 represent situations in which respondents drove with their knees placed on the steering wheel,
and legs crossed, respectively, when Autopilot was engaged
3.1.7. Hands-free driving
This sub-theme covers incidences of hands-free driving with Autopilot engaged, with respondents removing
their hands from the steering wheel longer than is technically allowed by the system.
Hands-free driving for longer stretches of time was enabled by placing weights on the steering wheel to
satisfy the steering wheel torque requirement.
5
6
8
7
9
10
12
11
14
13
“It is hands off for me.
1
I have work arounds for everything where I don’t need
to pay attention as much.” (R033)
“You put a one- or two-pound weight under the steering wheel. I use that all
the time. So I have a tungsten bar that’s really heavy metal and then I attach
that with Velcro to the steering wheel and it thinks my hand are always
attached.” (R044)
“Honestly, this is what I do most of the time. I’ll actually have a little weight
that you can clip on to the steering wheel. This is my biggest complaint with
FSD; that they have allowed this to persist where you can just put a little
weight on the wheel that negates all the nagging that it does.” (R068)
“Autopilot – I rarely have my hands on the wheel because when I turn it on, I
know that it’s safe and I know I don’t really need to worry too much but I’m
always ready to intervene.” (R077)
“I have a little coin pursue three stacks of 50 pennies started 50 US heavies.
I found the perfect amount of weight and it’s not gonna snap it out, but it’s
going to keep it in a lot of power. And it’s small enough that I can grab it with
my hand. I only really use that on the highway.” (R094)
FSD Beta, on the other hand, reduced the likelihood of hands-free driving given its status as technology
under development and the corresponding need to constantly supervise the system.
“I’m hyper attentive of it. My hand isn’t just like on Autopilot, loosely hanging
on the wheel. With FSD Beta, my hand is gripping the wheel, ready to when it
tries to turn left or something.” (R045)
“FSD Beta – I even have a separate grip for the wheel then when I’m on
Autopilot. Both hands on the wheel, I might have to apply immediate torque
quickly.” (R063)
1
Respondent was asked whether Autopilot is a hands-free feature.
“My hands are on the wheel a lot more than Autopilot is. They’re always on
the wheel. Eyes are always on the road. I don’t like looking away, even for a
second.” (R066)
“I’ve seen a video recently of someone in Canada making videos and his
hands are in his lap. Clearly, he hasn’t experienced the things that I’ve
experienced because if he had, you wouldn’t do that. You understand that you
don’t have the time to not have your hands on the wheel. Sometimes things
will happen very quickly.” (R096)
3.1.8. Mind-off and fatigued driving
This sub-theme covers instances of mind-off and fatigued driving associated with using Autopilot in
comparison to manual driving, with respondents reporting to engage in mind wandering to nodding off
behind the wheel. Respondents were prone to fall asleep on long-distance drives as the result of overtrusting
the capability of the system proven over time, negligence, or necessity to drive even though their mental
capabilities did not match the demands imposed by the driving task.
“After 17 or 18 hours of driving, I just did the little nod where it happened
very quickly. I know I was completely awake again and I was like ‘OK, well,
here’s the time where I have to take the weight off.’” (R068)
“I can’t say I haven’t nodded off with Autopilot engaged. I’ve have driven a
lot while being tired over the years from doing side work and there are times
where I’m used to that nodding off at the wheel. My brain tends to jerk myself
awake. Usually, my hands are on the wheel, so they are giving the car
feedback. So the car itself is not aware that I have nodded off.” (R071)
“When you have Autopilot, it’s your subconscious driving while you can think
of other stuff. Your brain is focused differently on driving while being safe.
You’re driving and then you come out of a thought and you’re like ‘How did
I get here? I don’t remember driving this part’. With Autopilot, it’s driving
like that all the time because you’re able to think of other stuff without being
fully concentrated on driving.” (R073)
“I’ve fallen asleep while on Autopilot before. It was really scary. I woke up. I
immediately pulled over. I’d say it’s pretty impossible to sleep on FSD Beta.”
(R074)
“I’ve actually nodded off using FSD on long highway drives. In those regards,
I’m confident, but I would never do that when there’s cars around. Where we
live, you can literally see 10 kilometers down the road and there’s no car. It’s
just straight. That’s when I could relax, and I was impressed. I was a little
embarrassed to tell people that I had done that because people raised their
eyebrows ‘You did what?’ If I saw any cars, no, I was paying attention.”
(R081)
3.1.9. Ability of taking over control
This sub-section covers drivers’ ability taking over control with Autopilot and FSD Beta engaged.
Respondents mentioned that they were more likely to stay prepared to take corrective actions with FSD
Beta than with Autopilot engaged.
“For Autopilot, I’d be guilty of not being prepared to take corrective action
100% of the time. A big part of the reason I love Autopilot is I don’t have to,
but for FSD Beta I would say ‘Yes, I am prepared to take corrective action at
all times’.” (R012)
“My hand is on the wheel. My foot is on the floor. I am watching the road. I
can take corrective action at any moment but there’s a very different state of
mind from Full Self-Driving ready to take corrective action. I am almost
sitting there tense, my hand is maybe at the same place for Autopilot but with
Full Self Driving, I’m gripping the steering wheel, it’s ready to go. I have a
foot over one pedal or the other, depending on whether I think it’s going to be
from too slow or too fast.” (R018)
“I certainly do that on FSD Beta. I definitely do for all the reasons I’ve said
before. But Autopilot – I feel like I’m typically less prepared because I’m more
relaxed. I’m more letting my guard down because I trust it more. It’s never
done as much wrong as it has on FSD Beta. I’m looking at the scenery, I’m
enjoying the ride. I’m enjoying the ride versus driving pretty much. So
definitely less prepared on Autopilot.” (R048)
“I typically stay prepared to take corrective actions. So with Autopilot, not
necessarily because if vehicles are braking, it’s really good at predicting the
braking as needed. Lane changes – it takes 30 seconds for it to make a lane
change, so it’s more of the system knows when it’s able to do so safely, so I
just let it do it. Obviously, Beta. You always have to be ready to take over at
any time. Again, my feet and hands are always ready to take over, so with FSD
always usually prepared to take over.” (R075)
“Autopilot – I would not see I’m prepared to take corrective action ‘cause
there’s not a hugely a corrective action elicited requirement. Full Self-Driving
Beta – your hands are on the wheel. Your foot’s over the brake, your hands
over the stock. You have all three ways to murder it to turn it off at your
disposal, and you’re actively ready to do.” (R084)
The placement of feet when Autopilot is engaged was reported to be more relaxed compared to FSD Beta.
With both systems engaged, respondents mentioned that they placed their right foot in a hovering position
over the accelerator rather than on the brake to be able to react to unexpected system behavior, such as
phantom braking.
“It’s pulled back like whatever is most comfortable on those long highway
rides. It’s definitely not always over the brake pedal. For FSD Beta, you
actually have to use the accelerator often because they use the accelerator to
give the system confidence. You can use the accelerator, move it along. If not,
my foot is over the brake. So a lot of times my foot is so the whole time using
FSD Beta.” (R002)
“FSB Beta – I’ll keep my foot right above the accelerator, ready to hit the gas
or the brake. Autopilot – I’ll put my feet flat on the ground. I won’t have them
sitting on top of the accelerator on, I’ll have him relax. If you would set cruise
control, same thing.” (R043)
“Especially on long trips, I will often take my shoes off. If I’m driving on a
long drive and it’s a dual carriageway divided and it’s nighttime, I know
there’s gonna be almost no chance of a phantom brake because there’s no
shadows and there’s no oncoming traffic. I know, I shouldn’t, but sometimes
I’ll sit cross-legged on the driver’s seat.” (R044)
“Yeah, with Autopilot, I’m pretty relaxed. I got my left foot to the far-left side
of the footwell, it’s got a little foot rest built into the car right there. On Beta,
my left foot is still resting off to the side, but my right foot is mostly hovering
over the accelerator more than it’s hovering over the brake because the car
has phantom braking.” (R048)
“FSD Beta – I usually have my foot hovering over the accelerator because it
is more likely to phantom brake or slow down than anything. Autopilot, If I’m
on a freeway stretch for a long time and I’ve driven it many times before, I’ll
pull both my feet back into like a normal sitting position.” (R055)
3.1.10. Skill degradation
This sub-theme covers the loss of driving skills associated with using Autopilot, with respondents reporting
to feel uncomfortable driving manually because they have been used to driving with the system automating
a part of the driving task.
“I would be very uncomfortable taking any long-distance road trip without
Autopilot. I probably wouldn’t take it in a car unless I absolutely had to.”
(R012)
“A few months ago, I drove a friend’s car and it was just a regular car. It was
a road trip and I just remember being so focused on the road and I felt like I
couldn’t even turn my eyes away from the road because it was so scary.”
(R027)
“It’s really hard for me to get into the traditional car. I feel really safe in a
Tesla. Whenever I’m going in the mountains here in Colorado, not ever having
to touch the brake pedal when you’re going down a hill and letting
regenerative braking slow you down and doing so in a very controlled
manner, makes me feel very safe, but most importantly in control. The way I
feel when I’m in a traditional car and I’m coasting because I’m going
downhill or coasting and having to brake, I feel extremely out of control of the
car.” (R065)
“As soon as I have to take over, I feel very uncomfortable for some reason. I
used to be very comfortable driving on my own.” (R074)
3.2. Direct in-vehicle modification of the driving task
3.2.1. Situational awareness
This sub-theme covers the changes in drivers’ situational awareness in comparison to manual driving.
Respondents mentioned an increase in situational awareness associated with using Autopilot, as the eyes
could be placed on the surroundings of the vehicle.
“I would even argue that it allows you to pay attention with more detail to
what’s happening around you, to watch the other drivers, and actually
monitor the other lanes a little bit more. So it appears that you have a
situational awareness that I don’t believe you have when driving on your
own.” (R001)
“This one’s more geared towards Autopilot. Being more aware and more alert
for long drives. So just kind of like Autopilot with airplanes, you have a little
more freedom to be looking around and checking your environment, your
surroundings.” (R046)
“Number one benefit is not having to just pay attention as much to the small
fine motor movements, sticking into the center of your lane. You get to pay
attention to the nearby traffic, pay attention to the cars around me much more.
It frees up my capacity, pay attention to others.” (R065)
As noted before, drivers’ situational awareness might also drop due to an overreliance on the system, the
dual role of the driver transitioning to being a passenger with the systems engaged, complacency, hands-
free, and mind-off and fatigued driving.
3.2.2. Workload
This sub-theme covers changes in mental and physical workload, with Autopilot contributing to a reduction
in workload and driver fatigue. Using the system made driving easier and more relaxing as drivers were no
longer required to perform most of the tactical and operational part of the driving task, and to monitor the
driving task permanently.
“Autopilot took a lot of extra load off the driver. You basically didn’t have to
process as much and weren’t as mentally strained to do long drives.” (R041)
“Why do I use Autopilot on the highway? Just because it’s a lot easier, a lot
less brain work. I’m a computer programmer. I use my brain all day. I don’t
want to use it drive it on the highway all day. I’d like a break.” (R045)
“Autopilot will deviate driver fatigue. The largest thing I noticed is just took
so much of the mental workload of driving off my brain. I didn’t need to worry
about what speed I was going, about how fast the car is ahead of me were
going, about maintaining my lane anymore. Those are all mental tasks that
are part of driving that I no longer need to worry about.” (R054)
“The base Autopilot is very helpful on the Interstate for reducing driver
fatigue. It’s a mental stress reliever because you don’t have to do the micro
corrections, it’s doing that for you.” (R090)
FSD Beta, on the other hand, increased mental workload given its status as a developing technology and
the corresponding need to constantly supervise the system as it could potentially do the wrong thing at the
worst time. Respondents had to monitor the system and be ready to intervene and take over control anytime,
resulting in a high disengagement rate.
“FSD Beta, my disengagement rate is probably four or five disengagements
per mile. Yesterday, I went to work and back and for 11-mile round trip it was
43 disengagements. There’s barely 43 intersections in my drive. As Autopilot
tries to take over more tasks, it can actually be more work for me. It was just
a straight road.” (R007)
“Autopilot – I engage because I’m tired and FSD Beta I won’t use if I’m tired.
I use FSD Beta where I know I don’t really need to give it a lot of energy. FSD
Beta takes a lot of energy. Imagine having a 12-year-old on your lap. ‘Get off
my lap. I don’t have the energy for you right now.’ It’s doing certain turns and
then it gets confused or stuck. ‘Yes, it’s OK to go ahead here, little child.’”
(R012)
“FSD Beta – it’s certainly very different in the way that I engage with it
because I’m using it not as a relaxing thing as I would Autopilot. I’m using it
more like a job. It could do the wrong thing at the wrong time. I really just
have to keep an eye on. I have to kinda hover over it.” (R048)
“With FSD Beta, I see a lot of disengagement on the trip, I just disengage it
and drive away, because at some point it becomes dangerous, I think, and it’s
easier for me. I get frustrated. Like ‘What are you? Why? Why are you doing
this?’ ‘What’s the point of doing this?’ It’s just unnecessary.” (R058)
“Yes, I’m constantly like clicking the gas and pellet pushing the gas in the
pellet to keep going. It’s just a lot of work. It made no sense to use.” (R090)
3.2.3. Stress
This sub-theme covers differences in stress while driving when Autopilot and FSD Beta are engaged.
Autopilot contributed to a decrease in stress while driving due to its consistently reliable performance of
keeping the vehicle within its lane and maintaining a safe distance to the car in front.
“I would turn on Autopilot and it would take all of the stress away. I didn’t
have to worry. It was smoothly keeping up with traffic and do well.” (R018)
“Why do you use Autopilot? On the highway, I use it because it takes the stress
out of normal driving up. When I drive on the Interstate with my very old car,
stop and go traffic can be very stressful. You can even feel the adrenaline go
up through your arm if you miss something and all of a sudden you get
startled. I don’t ever get startled with the Tesla driving with Autopilot on the
highway.” (R031)
“So I do use Autopilot frequently. I do feel less stressed when it’s operating, I
know it’s gonna stay in my lane. It’s not gonna hit the car in front of me. So I
can then get on the touch screen and find the station I wanna listen to or other
things I probably shouldn’t be doing while driving.” (R071)
FSD Beta, on the other hand, increased the stress while driving due to its technological state as Beta
technology and the corresponding need to constantly supervise the system. Respondents described the
system as a “drunk toddler”, “student teenage driver” and “babysitting” FSD Beta.
“Autopilot allows me to relax. FSD not so much. It’s more like I’m a babysitter
a little bit.” (R027)
“If I’m on a casual drive and I don’t want to think, I will drive manually. With
Full-Self driving you have to think more as a Beta tester because it’s not done,
so you have to be ready to take over. So it adds an extra level of stress and
you have to be more attentive. You have to pay a lot more attention. So because
of that, I do take breaks from using FSD Beta.” (R036)
“Just like Autopilot in an aircraft. It lets you relax a little bit so now you’re
not having to directly fly the plane, but you still monitor. With Beta typically,
when I turn it on, it adds more stress.” (R096)
3.3. Modification of travelling
3.3.1. Exposure
This sub-theme covers the increase in the amount of travelling associated with using Autopilot, with
respondents reporting to drive long-distances when Autopilot is engaged.
“It’s definitely made drives that otherwise would have been impossible. I went
to Texas by myself, 1400 miles each way. Doing that distance by myself over
the course of like a day and a half, I don’t think I could have done that in a
car without driver assistance features and especially at the level that Autopilot
provides.” (R005)
“We did this 3100-mile road trip to Florida. We did a 4500-mile road trip to
Texas. We did an 1800-mile road trip to Harrison back and we’ve done a
bunch of trips to the Hudson Valley and that’s just in the last year and all of
those trips were made possible because of Autopilot.” (R012)
“Autopilot just makes a long drive not long. I don’t stress about how long I’m
going or traffic or anything like that. I don’t care about any of that stuff on
Autopilot. So that part, it’s really awesome.” (R042)
“I also realized that when I get to my destination, I’m way less exhausted. The
one of the drives I recently did, I was able to sleep for six hours and drive for
18 to 20 hours and arrive at the destination wide awake, right?” (R054)
“So inherently I feel vastly safe with Autopilot. I feel 5X more safe driving so
much so that I’m willing to make more road trips and I’m willing to take
longer road trips.” (R086)
3.3.2. Route choice
This sub-theme covers changes in route choice associated with using FSD Beta. Given the Beta nature,
respondents reported to use the system to test it, e.g., in challenging situations, to contribute to the
development of the system.
“I’ll just drive the majority of the time that I use FSD Beta to test something.
I have a couple of standard routes that I do and then sometimes I’ll use it if
I’m in a new area and I wanna see how it’s gonna handle something.” (R051)
“I only use Beta like I did it this morning. It’s Sunday morning 6:30. I was
just plotting trips to see how it could handle, and how it did without any people
around.” (R068)
“I just use FSD Beta to unwind in the evening. I have an app on my phone,
and I have a couple 100 addresses in town, and it just randomly shuffles where
it’s gonna drive to and so I literally just drive around town and I listen to
music or podcasts to unwind that evening and just relax and enjoy the joy, the
drive. Look for edge cases that I have to correct.” (R085)
“FSD Beta I pretty much only engage it on specific test routes that I know how
the car has performed and I’m trying to do a comparison so I can get an idea
of how it’s functioning and what improvements I’m seeing. I pretty much do
like planned routes where I can test situations with it.” (R094)
4. Discussion
This study reports 103 interviews with drivers whose cars were equipped with Tesla’s FSD Beta and
standard Autopilot to investigate the indirect modification of user behavior, direct in-vehicle modification
of the driving task, and modification of exposure and route choice.
The interviews resulted in both expected and unexpected findings, being largely consistent across
individuals, which were structured in three main categories, and fifteen sub-categories. The three main
categories were the indirect modification of user behavior (10), direct in-vehicle modification of the driving
task (3), and modification of travelling (2) mentioned by at least five from 103 respondents.
The indirect, unintended modifications of user behavior (10) were a reduction in aggressive driving with
Autopilot engaged; the dual role of the driver transitioning to being a passenger in the car; overreliance on
Autopilot; using Autopilot in ODDs for which it was not designed; complacency (eyes-off road driving);
one-hand driving, hands-free driving; mind-off and fatigued driving; an improved ability of taking over
control with FSD Beta engaged; and skill degradation resulting in drivers being uncomfortable without
using automation.
The direct in-vehicle modification of the driving task (3) pertained to an increase in situational awareness
with Autopilot engaged, a decrease in mental and physical workload and stress with Autopilot engaged, but
an increase in workload and stress with FSD Beta engaged.
The modification of travelling (2) pertained to more (very) long-distance trips with Autopilot, and a change
in route choice with FSD Beta engaged.
The three sub-categories mentioned most often were a decrease in workload with Autopilot engaged, an
increase in one-hand driving, and using Autopilot in ODDs not designed for, with 63%, 53%, and 43% of
respondents mentioning these sub-categories, respectively. The sub-categories mentioned most frequently
may represent the most significant and prevalent behaviors of human drivers in partially automated cars,
some of which are already well-documented (e.g., reduced workload, see section 4.1.2 below). However,
this does not necessarily mean that sub-categories mentioned less frequently are of minor importance for
Human Factors researchers and professionals (e.g., the sub-category ‘mind-off and fatigued driving’
represents an undocumented yet highly safety-critical behavior).
4.1. Direct in-vehicle modification of driving task
4.1.1. Situational awareness
In line with expectations, the results revealed an increase in situational awareness with Autopilot engaged
in comparison to manual driving. Drivers reported to be able to monitor the vehicle surroundings more,
which they considered a key advantage of using Autopilot compared to manual driving. This reflects
studies, which have shown that respondents identified observing the scenery or landscape as one of their
favorite activities during automated driving (Nordhoff et al., 2021; Pfleging, Rang, & Broy, 2016).
Furthermore, this corresponds with studies reporting increased situational awareness when automated
driving was engaged (De Winter, Happee, Martens, & Stanton, 2014; Endsley, 2017). However, the role of
the driver transitioning to being a passenger with the systems engaged, cases of overreliance, complacency,
hands-free, mind-off and fatigued driving may diminish drivers’ actual situational awareness, even when
they report increased situational awareness.
Respondents reported to place their eyes more on the vehicle surroundings with Autopilot engaged and
more on the road ahead with FSD Beta. More dispersed visual attention and longer times spent watching
the driving scene have been associated with a higher situational awareness during automated driving (Liang
et al., 2021). The present study did not discriminate the three levels of situational awareness (i.e., perception
of the environmental elements and events; comprehension of meaning and projection of status in future)
(Endsley, 1995). A high situational awareness on three levels is essential to successfully take over control
from the car in critical transitions (Zhou, Yang, & De Winter, 2021). We recommend future research to
investigate all levels of situational awareness objectively over time in real driving conditions (Liang et al.,
2021; Zhou et al., 2021).
4.1.2. Workload
This study found the expected reduction in physical and mental workload when Autopilot was engaged,
reducing driver fatigue and increasing relaxation due to Autopilot taking over tactical and operational parts
of driving on highways. This corresponds with company reports (Tesla, 2022b) and ample scientific studies
reporting a reduced objective workload (see a metastudy by De Winter et al 2014; Heikoop, De Winter,
Van Arem, & Stanton, 2019), and subjective workload (only for automation-experienced drivers) (Stapel
et al., 2019). Hardman (2021) revealed that Autopilot users reported to feel less mentally and physically
strained during and after travelling with Autopilot. Where many studies report a reduced workload with
automation, Stapel et al (2019) found an increased objective workload in particular in complex traffic with
Tesla Autopilot. This increased objective workload was associated with active monitoring, and is somewhat
comparable to the increased attention and workload now reported with FSD Beta. Respondents in the
present study were early adopters with a strong technical or professional background and high level of
technology savviness, which may also explain the low subjective workload. Studies have shown that
cognitive underload can be detrimental to drivers’ take-over performance (McWilliams & Ward, 2021).
Hence, it is debatable whether the expected improved ability to take-over as reported by our respondents is
realistic. In comparison to Autopilot, FSD Beta increased workload as unfinished automated driving
technology and the corresponding need to constantly supervise the system, being prepared to take over
control anytime as the system may do the wrong thing at the worst time.
4.1.3. Stress
Respondents reported a decrease in stress when Autopilot was engaged due to Autopilot taking over the
lateral and longitudinal part of the driving task on highways. This reflects studies reporting a decrease in
stress during partially automated driving (Hardman, 2021; Heikoop et al., 2019). FSD Beta, however,
increased stress while driving. We recommend future studies to investigate to what extent two systems or
ODDs imposing totally different cognitive demands on drivers affect drivers’ ability to monitor automation
and intervene in critical situations over time.
4.2. Indirect modification of user behavior
The use of Autopilot and FSD Beta induced some indirect, unintended, and potentially dangerous
behavioral changes of drivers. Some represent knowing violations of intended use (e.g., weighting the
steering wheel, using Autopilot in ODDs not designed for), and others reflect misunderstanding or lack of
experience (e.g., using Autopilot in ODDs not designed for).
4.2.1. Using Autopilot in ODD’s not designed for
Respondents reported to use Autopilot in operational design domains for which it was not designed due to
a lack of knowledge on the ODDs in which it can be used, overtrust, apparent system competence, or to
experience and test the limits of the system. Previous research supported the use of Autopilot in ODD’s for
which it was not designed (Kim, Song, & Doerzaph, 2021), which may represent a safety risk. Educating
drivers via the user manual may be insufficient as manuals are rarely consulted to gain information about
system capabilities and limitations (Kim et al., 2021), and may be too technical for non-technical users.
Driver training programs may need to be established (Kim et al., 2021), and system limitations can be more
effectively communicated via Human Machine Interfaces (Capallera et al., 2019). However, as a correct
understanding of system capabilities and limitations does not guarantee safe use, safe use may need to be
“established” by design, i.e., punishing misuse by deactivating the system for a predefined period, e.g.,
Autopilot Jail (Reddit, 2022b)
4.2.2. Complacency (eyes-off road driving)
The present study provides evidence for complacency with Autopilot but not with FSD Beta. Respondents
indicated to become complacent over time, taking their eyes off the road for relatively long stretches (e.g.,
44 miles without looking up), and engaging in secondary activities (e.g., working on laptop). In line with
Hardman (2021), the study revealed that drivers of partially automated driving systems felt like passengers
supervising rather than actively controlling the vehicle during automated driving. This may increase the
likelihood of complacency and hamper the ability to take over control in safety-critical situations. This
concurs with other studies in partially automated driving reporting drivers taking eyes off the road
(Morando, Gershon, Mehler, & Reimer, 2021; Solís-Marcos, Ahlström, & Kircher, 2018), and engaging in
secondary activities (Banks et al., 2018; Endsley, 2017; Kim et al., 2021; Metz et al., 2021; Wilson et al.,
2020).
4.2.3. One-hand, hands-free, mind-off and fatigued driving
Our study found evidence of one-hand, hands-free and mind-off driving. Studies have provided empirical
evidence for users of Autopilot providing low or even no steering wheel control (Banks et al., 2018; Kim
et al., 2021; Morando et al., 2021). Our study further enriches the literature, providing evidence for actively
manipulating the steering wheel control by weighting the steering wheel to indicate driver availability.
Mind-off driving was also observed, with drivers reporting to engage in mind wandering or even falling
asleep behind the steering wheel when Autopilot was engaged. Mind wandering is more likely to occur
during monotonous (Eastwood, Frischen, Fenske, & Smilek, 2012), easier or longer tasks (Smallwood &
Schooler, 2015). Ahlström et al. (2021) found that partially automated driving had a small effect on fatigue
during daytime, but increased the likelihood of increased sleepiness during night-time.
4.3. Modification of exposure and route choice
Using Autopilot has contributed to (very) long-distance travelling due to safety and convenience benefits,
which concurs with studies conducted for partially automated driving (Hardman, Chakraborty, & Tal,
2022). An increase in vehicles miles travelled has also been found for conditionally automated driving
(Lehtonen et al., 2022). New safety risks may arise when the number of hours travelling by car with the
system engaged exceeds drivers’ mental and physical capacities to perform the driving task safely, i.e.,
respond to objects and events in the environment and take-over requests. Studies have shown that humans
have difficulties to effectively monitor automation for more than 30 minutes (Bainbridge, 1983). FSD Beta
contributed to a change in route choice given the interest and curiosity of its Beta users to test the system
in challenging situations, helping Tesla to develop the system and realize the dream of a driverless future.
An increase in the number of local trips due to Autopilot was evidenced before (Hardman, 2021). It is
plausible that these effects are temporary and disappear with system maturity.
4.4. Study limitations
First, the data extracted from the present study reflect the subjective perceptions of drivers, which may not
correspond to actual risk and safety.
Second, face-to-face interviews may produce biased responses due to the personal contact between
respondents and the interviewer, e.g., due to the tone of the questions asked and the facial expressions of
the interviewer (Bowling, 2005). This bias was reduced by developing the interview protocol with a set of
predefined questions, with respondents being able to steer through the questionnaire themselves during the
Zoom interview.
Third, self-selection bias is present with regards to participation in the study, entry into the FSD Beta
program, as well as the initial purchase decision that is alluded to entry in the FSD Beta program. FSD Beta
participants represent an exclusive group selected by Tesla in two stages, with Tesla granting access to FSD
Beta to pre-selected owners in the first stage (e.g., presidents of Tesla Owner clubs), and to drivers with a
high safety score in the second stage (Korosec, 2021; Lambert, 2022a, 2022b). As a result, the interest in,
enthusiasm for and positivity of respondents as early adopters of partially automated driving technology is
higher than in the general population. As early adopters, respondents may also be more willing to take risks
to test the limits of the system (Agarwal et al., 1998). We recommend future research to replicate the study
with a representative part of the population of drivers of partially automated driving systems.
4.5. Final conclusions
This interview study with 103 participants of Tesla’s Full-Self Driving Beta program, which extends the
ODD of standard Autopilot to non-highway roads, revealed that the use of Autopilot and FSD Beta resulted
in unintended positive and negative changes of user behavior. Drivers became complacent over time with
Autopilot engaged. They failed to monitor the system, and engaged in hands-free and mind-off and fatigued
driving, such as placing weights on the steering wheel and falling asleep behind the wheel with the systems
engaged. The risk of complacency and unsafe behavior was high in simple highway environments. The
effectiveness of the steering wheel torque sensor as driver monitoring technology was questioned. Testing
unfinished automated driving technology may place substantial demands on drivers who might be
unprepared to meet these demands. We recommend future research to investigate to what extent the
unintended negative behavioral changes increase the likelihood of being involved in a crash compared to
manual driving.
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6. Appendix
Table 1. Overview of the interview instrument; i.e., question number, question
Question
number
Question
Q1
Do you have the Full Self-Driving Beta (FSD Beta) feature? (1 = Yes, 2 = No)
Q2
Before the first time of using Autopilot and FSD Beta, did you watch / read / listen to information on how to
use it? (1 = Yes, 2 = No)
Q3
Please mention the type of information you consulted on how to use Autopilot and FSD Beta (website of Tesla
(www.tesla.com), car dealer / sales point, online communities and forums, YouTube videos, newspapers and
magazines, friends, family, colleagues, driver manual)
Q4
Please describe your experience with using Autopilot and FSD Beta and the benefits and risks associated with
using it. Please explain your answer.
Q5
Have your expectations of using Autopilot and FSD Beta been fulfilled? Why / why not?
Q6
Why do you use Autopilot and FSD Beta?
Q7
Did you ever stop using Autopilot and FSD Beta (for prolonged periods of time)?
Next, we would like to explore your perceptions regarding four general statements about the operation of Autopilot
and FSD Beta.
Q8
The current Autopilot does make driving autonomous. Is that correct?
(1 = Yes, 2 = No, 3 = I don’t know)
Q9
There are no safety issues with Autopilot. Is that correct?
(1 = Yes, 2 = No, 3 = I don’t know)
Q10
Autopilot is a hands-on feature. Is that correct?
(1 = Yes, 2 = No, 3 = I don’t know)
Q11
Tesla FSD Beta is safer than a human. Is that correct?
(1 = Yes, 2 = No, 3 = I don’t know)
With the next section, we would like to explore your perceptions of safety while using Autopilot and FSD Beta.
Q12
Do you feel safe when Autopilot and FSD Beta is active? Why / why not?
Q13
What / how do you feel when you feel safe / unsafe? Please explain.
Q14
What is it about Autopilot and FSD Beta that is safe / unsafe? Please explain.
Q15
Now please remember the situation / s in which you typically feel unsafe when Autopilot and FSD Beta is
active and describe these situations.
Q16
What can Autopilot and FSD Beta do to support your safety in Autopilot and FSD Beta? Please explain.
Q17
Does feeling safe / feeling unsafe impact how you use Autopilot and FSD Beta on your next drives / in the
future? Please explain.
Q18
Has your perceived safety changed over time? If so, how?
With the next section, we would like to explore your trust in Autopilot and FSD Beta.
Q19
How would you position your level of trust in Autopilot and FSD Beta.
(1 = I don’t trust it at all, 2 = I don’t trust it, 3 = I neither don’t trust it at all nor trust it a lot,
4 = I trust it, 5 = I trust it a lot)
Q20
What can Autopilot and FSD Beta do to support your trust in Autopilot and FSD Beta?
Q21
Does your trust / distrust in Autopilot and FSD Beta impact how you use Autopilot and FSD Beta on your next
drives / in the future? Please explain.
Q22
Has your trust changed over time? If so, how?
Q23
When you do compare yourself with other drivers, Autopilot, and FSD Beta, do you think you are ...
(1 = A much worse driver, 2 = A worse driver, 3 = Not a better nor a worse driver, 4 = A better driver, 5 = A
much better driver) (De Craen, 2010)
With the next section, we would like to explore how you typically use Autopilot and FSD Beta.
Q24
How do you typically place your hands on the steering wheel when Autopilot and FSD Beta is active? Please
select the image that serves as best representation of your placement of your hands on the steering wheel when
Autopilot / FSD Beta is active and explain your answer.
Figure is from Morando et al. (2021)
Q25
Do you typically keep your hands on the steering wheel at all times?
Q26
Are you typically fully attentive and alert at all times?
Q27
How often do you typically engage in other secondary activities while Autopilot and FSD Beta is active?
(Never, rarely, occasionally, frequently, always; monitoring the road ahead, talking to fellow travelers,
observing the landscape, using the phone for music selection, using the phone for navigation, using the phone
for calls, eating and drinking, using the phone for texting, watching videos / TV shows, sleeping)
Q28
Do you disengage Autopilot and FSD Beta? Why / why not?
Q29
Does Autopilot and FSD Beta disengage? When / in which situations?
Q30
How do you typically place your eyes when Autopilot and FSD Beta is active?
Q31
Do you typically keep your eyes on the road at all times?
Q32
Do you typically monitor the vehicle and its surroundings at all times?
Q33
How do you typically place your feet when Autopilot and FSD Beta is active?
Q34
Do you typically stay prepared to take corrective actions at all times?
Q35
Has your use of Autopilot (in terms of how you placed your hands on the steering wheel, eyes on the road, and
feet) changed over time? If so, how?
