Factors Influencing and Contributing to Perceived Safety of Passengers during Driverless Shuttle Rides
1.1. Perceived Safety in AVs
1.2. Study Design
- A Level 4 and especially Level 5 AV would not need a human driver or steward, and a passenger could potentially be alone in an autonomous shuttle, which can influence perceived safety . Passengers would need to trust the technology of the automated system and would have no way to speak to a human driver or steward directly.
- Building on findings from public transport, being alone with unknown people is one of the greatest sources of anxiety . People are especially concerned about safety inside an autonomous shuttle , as they worried of being harassed or threatened when there is no driver or steward to potentially intervene . This characteristic of the lack of a human driver or steward is a potential challenge for perceived safety, therefore, we designed a test ride with a person who behaves obnoxious and is not pleasant to share a ride with.
- If automated systems are not working properly, people are hesitant to use them . In case of situations of technical problems in an autonomous shuttle, passengers would need to trust technology for a safe continuation of the journey or a resolution of the problem. Technical limitations and difficulties are challenging for perceived safety, especially with AVs as a new technology, as people are skeptical about the reliability and technical aspects of AVs already . With the autonomous shuttle we used, we identified two situations where technical difficulties might be happening in future use.
2. Materials and Methods
2.1. Shuttle and Test Area
2.2. Recruitment and Instruction of Passengers
2.3. Description of Test Rides
- Test ride 1 (riding as single passenger): The task for the passenger was to ride the autonomous shuttle alone (no steward or driver present). The instruction to the passenger was to ride the driverless shuttle on his or her own from a starting point to a predefined stop.
- Test ride 2 (interacting with another passenger): The aim of the second test ride was to explore perceived safety with other passengers on board. The instruction was to ride from a starting point to a predefined stop. This time, an actor (member of the research team), posing as an annoying passenger entered the shuttle. As soon as the shuttle departed, the actor started to behave in an unpleasant manner. He listened to loud music, situated himself closely to the passenger and gesticulated wildly in order to provoke a small-to-modest inconvenience.
- Test ride 3 (capacity management/technical difficulties): Test ride 3 dealt with capacity limits of the shuttle. Several passengers, exceeding the number of permitted passengers (six), were given the task to ride from a starting point to a predefined stop or to get on an already full shuttle. Passengers had the option of either entering the shuttle regardless of the overcrowded conditions or waiting until the shuttle returned.
- Test ride 4 (emergency/technical difficulties): The aim of this test ride was to learn about passengers’ perceived safety in case of a sudden, unexpected stop during the test ride between two stops. Six passengers at a time were asked to ride from a starting point to a predefined stop. The shuttle stopped during this journey abruptly and unexpectedly. After 60 s, an announcement was made indicating the detection of a technical problem and the continuation of the ride after correction of the defect. If the passengers contacted the control room before the expiration of the 60 s, no announcement was made. If the passengers did not show any reaction 120 s after the announcement in form of contacting the control room or leaving the shuttle, the announcement was repeated every 30 s. After approximately 6 min, the shuttle continued its ride and drove the remaining passengers to the predefined stop.
2.4. Questionnaires and Coding of Answers
3.1. Factors That Influenced Perceived Safety
3.2. Suggestions for Increasing Perceived Safety
3.3. Results of Test Rides
Limitations of the Study
- The main conclusions of our explorative study are that driving style of the shuttle and trust in technology were significant factors that influenced passengers’ perceived safety.
- Readily available contact with someone in a control room would significantly contribute to an increase in perceived safety while riding a driverless shuttle.
- While driving style was important, it was mentioned less as passengers got experienced in use with the shuttle.
- For researchers as well as technicians in the field of autonomous driving, our findings could influence the design and set-up of driverless shuttles in order to increase perceived safety, for example, how to signal passengers that there is always contact to someone in a control room possible who is assisting (not only) in the case of an emergency, or to explore the best way to instill trust in the technology of AVs in passengers. With attention to concerns of potential passengers and more experience of passengers in shuttles, this will help to foster acceptance of AVs in society.
- Future research should explore our findings in an even more natural setting, e.g., a controlled mixed traffic environment with dynamic traffic situations.
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
- Your age:
- Your gender:
- Do you have any knowledge about automated vehicles? (single choice format)
- Yes, I have in-depth knowledge about it.
- Yes, I have a basic understanding.
- Yes, I have heard about it.
- How save did you feel during the ride? (single choice format)
- Very safe
- Less safe
- Not safe
- Which factors had an effect on your feeling of safety? (open-ended question)
- What could increase your feeling of safety? (open-ended question)
- In which situations would you use an audio or a video connection to someone in a control room?
- For information on the route and schedule. (yes/no)
- For information on connections en route. (yes/no)
- In case of unexpected stops of the vehicle. (yes/no)
- In case of harassments from other passengers. (yes/no)
- In emergency cases. (yes/no)
- What factors would you consider necessary for the automated shuttle to be safe in future traffic?
- The automated shuttle drives in its own lane without other road users around. (yes/no)
- The automated shuttle behaves just like a shuttle with a human driver. (yes/no)
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Luger-Bazinger, C.; Zankl, C.; Klieber, K.; Hornung-Prähauser, V.; Rehrl, K. Factors Influencing and Contributing to Perceived Safety of Passengers during Driverless Shuttle Rides. Future Transp. 2021, 1, 657-671. https://doi.org/10.3390/futuretransp1030035
Luger-Bazinger C, Zankl C, Klieber K, Hornung-Prähauser V, Rehrl K. Factors Influencing and Contributing to Perceived Safety of Passengers during Driverless Shuttle Rides. Future Transportation. 2021; 1(3):657-671. https://doi.org/10.3390/futuretransp1030035Chicago/Turabian Style
Luger-Bazinger, Claudia, Cornelia Zankl, Karin Klieber, Veronika Hornung-Prähauser, and Karl Rehrl. 2021. "Factors Influencing and Contributing to Perceived Safety of Passengers during Driverless Shuttle Rides" Future Transportation 1, no. 3: 657-671. https://doi.org/10.3390/futuretransp1030035