Promoting Trust in Autonomous Vehicles: The Effects of Personality on Trust

Autonomous vehicles (AVs) have the potential for a far-reaching positive impact, if they are implemented within an accepting social climate and under appropriate regulation. They are predicted to bring a safer, more efficient, and more sustainable transport. However, despite the extensive positive implications of AVs, 71 per cent of the general public state that they would be afraid of getting a drive in one. This scepticism is a problem because public perception can hinder legislation, which is important in enabling autonomous vehicles to even become available. Moreover, trust and acceptance influence whether people will actually use the autonomous vehicle, and so they also have an impact on adoption.

The first experience with an autonomous technology is very important, because there is a positive feedback loop between usage, acceptance, and trust. Many drivers will have the opportunity for a first hands on experience with autonomous cars in the coming years. Level 4 AVs are predicted constitute between 10.3 and 33.8 per cent of all vehicles on the road by 2030. Level 4 automation represents full autonomy in certain scenarios such as motorways and manual control in others like cities. There will therefore be a moment in everyday driving when the driver will be able to hand off control of the vehicle to the autonomous system. This involves the loss of control and requires trust.

Previous research has identified a link between personality traits and trust in automation. However, research into influence of personality on trust behaviour has been inconclusive. Trust behaviour is behaviour that demonstrates a reliance on the autonomous system. It happens when the trustee accepts vulnerability and engages in risk taking behaviour within the context of the autonomous system. This study examined whether personality traits can influence trust behaviour in the context of autonomous driving.

Communicating the autonomous system’s decisions to the user increases trust in AVs. Utilisation of AR technology has been found especially effective, because it provides a more true-to-life and immersive experience than regular displays. The secondary aim of this study was to examine whether these positive implications of AR on trust are present during the transition of control, which is a crucial part in the trust-building process and will be more commonplace in the coming years.

The study was created in the form of an app, using Unity 3D game engine. It was available on Apple App Store and Google Playstore. Data from forty-seven participants was collected. They answered a set of questions and took part in two simulations.

To measure behavioural trust, participants need to be engaged in a situation where they can act as they please, and their behaviour can be observed. For this purpose an OpenVR simulation was developed. In OpenVR, the participant holds their mobile device, which provides a ‘window’ to the virtual world.

An important concept to consider when designing VR simulations is presence, which relates to whether participants react to stimuli in the simulation the same way as they would in real life. For this the simulation needs high psychological fidelity. To ensure high psychological fidelity of the driving experience, a realistic traffic system was developed that closely matches the European road style. Traffic sign and lane sizes, traffic sign distances to crossroads, and traffic light timings were kept compliant to regulation.

In the simulation the participants were tasked with driving to a destination in a Level 4 autonomous vehicle. The drive started in a city, where automation is not available. They navigated out of the city and onto the motorway. After reaching the motorway, which is a context where full automation can be utilised, they were able to choose whether to engage the autopilot. The time to engage the system was measured from the point when autonomy was made available to the point when it was engaged. This was the measure of behavioural trust.

The results suggest that there is a link between personality traits and trust behaviour in the context of AVs. Specifically, openness to experience positively predicted behavioural trust, whereas conscientiousness negatively predicted behavioural trust. Openness reflects the extent to which an individual desires change, and variety, whereas conscientiousness is the extent to which one is dependable, and responsible. The results suggest that trust is an enduring trait rather than a transient state and relates to people’s underlying individual differences and it can affect behaviour.

AR was found to be beneficial in building trust in AVs. The results suggest that the potential of AR for enhancing trust in autonomous systems can be extended into the transfer-of-control stage, and also imply that AR displays could be used to increase engagement rate.

The results indicate that personality might need to be considered when designing autonomous driving systems. Tailoring the systems and in-car HMIs to the user’s personality could have the potential to improve trust. The findings suggest that AV systems could also be tailored to calibrate trust, in order to prevent misuse or disuse. It can be concluded that providing the driver with information about how the autonomous system functions and why it performs actions is important to reassure them of the system’s competence. All these findings are valuable to consider when designing an AV interface to promote trust and in doing so push the transition forwards toward fully autonomous transport.