1 Introduction
2 Literature review
3 Definitions of distrust, TTFs, and scenarios
3.1 Definition of distrust in automated vehicles
3.2 Rationale underlying TTFs
Adoption/exclusion | Reason for adoption/Exclusion | Main Cause of TTF (bold font: adopted TTF in this study) | Similar causes | Definition |
---|---|---|---|---|
Adopted in this study | No system problems occurred in automated mode | Lack of informationa (TTF1) | Anxiety about interacting with pedestrians and cyclistsb and anxiety about interacting with non-self-driving vehiclesb | Distrust due to lack of information about the surroundings and performance of automated system |
Out of controla (TTF2) | – | Distrust because the system assesses and functions on its own during operation without providing users with a choice | ||
Unpredictabilitya (TTF3) | Lack of confidencea, anxiety about self-driving vehicles getting confused by unexpected situationsb and anxiety about system performance in poor weatherb | Distrust due to suspicions about the ability of the automated system to respond to its surroundings | ||
Value incongruencea (TTF4) | Machine-likea and anxiety about self-driving vehicles not driving as well as human drivers in generalb | Distrust due to differences in driving styles between an automated system and human users in normal scenarios | ||
Excluded from this study due to our study scope | Automated system problems during automated mode | Functional incompetencea | Anxiety about safety consequences of system failureb | Distrust due to system and vehicle problems |
Anxiety about system securityb | Anxiety about vehicle securityb and anxiety about data privacyb | Distrust due to security failure of the system | ||
Automated system not in use | Fiduciary irresponsibilitya | Legal liability of usersb | Distrust due to the lack of clarity on the assignment of responsibility for an accident during automated driving | |
Anxiety about learning to use self-driving vehiclesb | – | Distrust due to problems caused by the user’s poor use of the system’s functions |
3.3 Proposal of information types to mitigate TTF
3.3.1 Recognition status of external objects (ICT1)
3.3.2 Location of external objects (ICT2)
3.3.3 User vehicle acceleration/deceleration (ICT3)
3.3.4 User vehicle location and projected path (ICT4)
3.3.5 Status of external objects (ICT5)
3.4 Suggestions for distrust-evoking scenarios in automated driving
4 Method
4.1 Study goal and hypotheses
4.2 Independent and dependent variables
Corresponding hypothesis | IV | Level | DV | Type |
---|---|---|---|---|
H1 | Distrust scenarios | 21 distrust events [jaywalker, pedestrian near the curb, lane sharing with bicycles, parked vehicles on the shoulder, rapid acceleration, two changes in direction, too close to the vehicle in front, vehicle accident, vehicle cutting in, large-scale bus moving out of the lane center, high traffic at a corner, incorrectly parked vehicle, vehicle exiting a parking lot, U-turn too sharp, too close to the curb, too close to another vehicle when turning, change in direction, traffic light turning yellow, lane recognition when entering a tunnel, too many pedestrians, and congestion when merging with a highway] | TTFs | TTF1 [–] TTF2 [–] TTF3 [–] TTF4 [–] |
H2 | Trust-threatening factors | TTFs [TTF1, TTF2, TTF3, TTF4] | ICT-specific necessity level | ICT1 [score] ICT2 [score] ICT3 [score] ICT4 [score] ICT5 [score] |
ICM-specific necessity level | ICM1 [score] ICM2 [score] ICM3 [score] |
4.3 Experimental procedure
4.4 Participants
4.5 Apparatus
5 Results
5.1 User distrust scenario analyses (H1)
5.2 User TTF-specific information configuration type and method (H2)
DV | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
IV | Information configuration type | Information configuration method | |||||||||
Recognition status of external objects (ICT1) | Location of external objects (ICT2) | User vehicle acceleration/deceleration (ICT3) | User vehicle location and projected path (ICT4) | Status of external objects (ICT5) | Total | Visual modality (ICM1) | Auditory modality (ICM2) | Haptic modality (ICM3) | Total | ||
Lack of information (TTF1) | Mean | 27.2 | 20.4 | 17.3 | 14.6 | 18.4 | 19.5 | 21.5 | 23 | 6.9 | 17.1 |
Median | 26 | 20 | 18 | 14 | 18 | 20 | 22 | 23 | 7 | 21 | |
Rank | 1 | 1 | 2 | 3 | 2 | – | 1 | 1 | 2 | – | |
Out of control (TTF2) | Mean | 22.8 | 19.3 | 16.5 | 20 | 15.2 | 18.8 | 20.75 | 21 | 4.75 | 15.5 |
Median | 22.5 | 19.5 | 14.5 | 21 | 15 | 18.5 | 21 | 21.5 | 4.5 | 19 | |
Rank | 1 | 1 | 2 | 1 | 2 | – | 1 | 1 | 2 | – | |
Unpredictability (TTF3) | Mean | 25.3 | 19.3 | 9.5 | 17.8 | 13.8 | 17.1 | 22.75 | 20 | 4.25 | 15.7 |
Median | 27 | 19 | 10 | 17.5 | 15 | 17 | 23 | 20 | 5 | 20 | |
Rank | 1 | 2 | 3 | 2 | 3 | – | 1 | 1 | 2 | – | |
Value incongruence (TTF4) | Mean | 21.6 | 16.4 | 15.4 | 13.2 | 12.8 | 15.9 | 22.2 | 18.6 | 3.4 | 14.7 |
Median | 20 | 18 | 13 | 14 | 14 | 15 | 22 | 19 | 3 | 19 | |
Rank | 1 | 1 | 2 | 2 | 2 | – | 1 | 2 | 3 | – | |
Mean | 24.2 | 18.8 | 16.7 | 16.4 | 15.0 | – | 21.89 | 20.7 | 4.8 | – | |
Median | 26 | 19.5 | 14.5 | 14 | 15.5 | – | 22 | 21 | 5 | – |
TTF | Kruskal–Wallis result | Bonferroni post hoc result | |||||
---|---|---|---|---|---|---|---|
1 [Lack of information] | H = 341.909, DOF = 4, p < 0.001 | ICT | ICT1 | ICT2 | ICT3 | ICT4 | ICT5 |
ICT1 | – | F = 186.926 p < 0.001* | F = 234.193 p < 0.001* | F = 367.225 p < 0.001* | F = 270.070 p < 0.001* | ||
ICT2 | – | – | p = 47.267 p = 0.024 | F = 180.330 p < 0.001* | F = 83.144 p < 0.001* | ||
ICT3 | – | – | – | F = 133.063 p < 0.001* | F = 35.877 p = 0.098 | ||
ICT4 | – | – | – | – | F = 97.185 p < 0.001* | ||
ICT5 | – | – | – | – | – | ||
2 [Out of Control] | H = 96.133, DOF = 4, p < 0.001 | ICT1 | – | F = 33.630 p = 0.012 | F = 89.433 p < 0.001* | F = 10.327 p = 0.430 | F = 97.299 p < 0.001* |
ICT2 | – | – | F = 55.803 p < 0.001* | F = 23.303 p = 0.065 | F = 63.669 p < 0.001* | ||
ICT3 | – | – | – | F = 79.106 p < 0.001* | F = 7.866 p = 0.538 | ||
ICT4 | – | – | – | – | F = 86.972 p < 0.001* | ||
ICT5 | – | – | – | – | – | ||
3 [Unpredictability] | H = 146.724, DOF = 4, p < 0.001 | ICT1 | – | F = 39.112 p = 0.004* | F = 141.141 p < 0.001* | F = 61.016 p < 0.001* | F = 112.117 p < 0.001* |
ICT2 | – | – | F = 102.029 p < 0.001* | F = 21.903 p = 0.083 | F = 73.005 p < 0.001* | ||
ICT3 | – | – | – | F = 80.126 p < 0.001* | F = 29.024 p = 0.023 | ||
ICT4 | – | – | – | – | F = 51.101 p < 0.001* | ||
ICT5 | – | – | – | – | – | ||
4 [Value incongruence] | H = 80.845, DOF = 4, p < 0.001 | ICT1 | – | F = 31.791 p = 0.024 | F = 97.631 p < 0.001* | F = 81.144 p < 0.001* | F = 105.546 p < 0.001* |
ICT2 | – | – | F = 65.840 p < 0.001* | F = 49.353 p < 0.001* | F = 73.756 p < 0.001* | ||
ICT3 | – | – | – | F = 16.487 p = 0.254 | F = 7.916 p = 0.593 | ||
ICT4 | – | – | – | – | F = 24.402 p = 0.090 | ||
ICT5 | – | – | – | – | – |
TTF | Kruskal–Wallis result | Bonferroni post hoc result | |||
---|---|---|---|---|---|
1 [Lack of information] | H = 240.456, DOF = 2, p < 0.001 | ICM | ICM1 | ICM2 | ICM3 |
ICM1 | – | F = 29.507, p = 0.025 | F = 154.858, p < 0.001* | ||
ICM2 | – | – | F = 184.365, p < 0.001* | ||
ICM3 | – | – | – | ||
2 [Out of Control] | H = 76.418, DOF = 2, p < 0.001 | ICM1 | – | F = 8.081, p = 0.280 | F = 64.183, p < 0.001* |
ICM2 | – | – | F = 56.102, p < 0.001* | ||
ICM3 | - | – | – | ||
3 [Unpredictability] | H = 80.723, DOF = 2, p < 0.001 | ICM1 | – | F = 15.054, p = 0.042 | F = 67.793, p < 0.001* |
ICM2 | – | – | F = 52.739, p < 0.001* | ||
ICM3 | – | – | – | ||
4 [Value incongruence] | H = 133.758, DOF = 2, p < 0.001 | ICM1 | – | F = 47.935, p < 0.001 | F = 100.435, p < 0.001* |
ICM2 | – | – | F = 52.5, p < 0.001* | ||
ICM3 | – | – | – |
5.2.1 Lack of information: TTF1
5.2.2 Out of control: TTF2
5.2.3 Unpredictability: TTF3
5.2.4 Value incongruence: TTF4
6 Discussion
DV | ||||||||
---|---|---|---|---|---|---|---|---|
IV | Information configuration type | Information configuration method | ||||||
Recognition status of external objects (ICT1) | Location of external objects (ICT2) | User vehicle acceleration/deceleration (ICT3) | User vehicle location and projected path (ICT4) | Status of external objects (ICT5) | Visual modality (ICM1) | Auditory modality (ICM2) | Haptic modality (ICM3) | |
Lack of information (TTF1) | All users | All users | Highly distrusting users | – | Highly distrusting users | All users | All users | Highly distrusting users |
Out of control (TTF2) | All users | All users | Highly distrusting users | All users | Highly distrusting users | All users | All users | Highly distrusting users |
Unpredict-ability (TTF3) | All users | Highly distrusting users | – | Highly distrusting users | – | All users | All users | Highly distrusting users |
Value incongrue-nce (TTF4) | All users | All users | Highly distrusting users | Highly distrusting users | Highly distrusting users | All users | Highly distrusting users | – |