# Modeling Driver's Real-Time Confidence in Autonomous Vehicles
## 2 Survey on Main Factors Affecting Confidence  
The survey of confidence in the use of autonomous driving systems was conducted among random members of the community who have had experience with autonomous driving systems. The first round of the survey was a small open-ended question asking \"What are the main reasons an autonomous driving system makes you feel less confident while driving? \". 15 interviewees responded to the question. The results were collated to generate a total of 15 confidence confounders, as follows:  
_Confidence Confounders_  
* AVs sudden acceleration, braking or turning
* Traffic participants' approaching
* Surrounding vehicles' sudden braking or acceleration
* Approaching scenarios like cross-road or tunnel
* Numerous buses or large trucks nearby
* Numerous pedestrian nearby
* Existence of blind zone
* Bad weather condition
* High velocity
* High-frequency lane change
* Poor brands with low prices
* Short system up-time
* Low volume production scale
* Unable to visualize perceptual or path info
* Small numbers or types of sensors  
Research has shown that a driver's driving characteristics can affect their driving confidence [16]. However, in order to facilitate the identification of more universally applicable factors influencing driver confidence, we did not take into account the driving characteristics of the drivers in our survey. Based on the main influencing factors, we constructed a large-scale study of drivers' confidence in their willingness to take over. 180 copies of the study were sent out and 135 were returned. Respondents were asked to give their confidence level for each factor, ranging from Level 1 to Level 5, with lower levels representing lower confidence and a higher probability of taking over. Level 1 indicates 0 scores, and Level 5 indicates 5 scores. The results of the study are shown in Figure 1. The confidence score in the figure is obtained by calculating the average. It can be seen from the figure that the proximity of other traffic participants to the ego vehicle has the greatest impact on driver confidence, with a mean confidence score of only 2.36. The second most influential factor is the sudden acceleration and deceleration or sharp turning and the frequent lane change of the ego, with a mean confidence score of 2.47. Other factors that have a greater influence are the high velocity of the ego, the large number of pedestrians nearby, and the sudden acceleration or braking of surrounding vehicles. Among the numerous factors, the behavior of the AV itself brings the most obvious confidence value reduction, followed by the influence of some surrounding participants or the environment. Furthermore, some inherent factors, such as automatic driving system manufacturers, vehicle brands, etc. will also have an impact on driving confidence but are lower compared to other reasons, for which confidence scores are above 3.3. Based on the results of our research, we identified three factors that affect the real-time confidence of human drivers in autonomous vehicles: (1) external traffic participant behavior, which is dominated by surrounding vehicles that may interfere with the ego vehicle; (2) the behavior of the ego vehicle, which is dominated by abnormal acceleration and deceleration; and (3) the complexity of the surrounding environment, which is composed of numerous complex attributes. To construct the relationships between the various types of influences, a reasonable framework is required. Driver confidence is a quantity that is continuously influenced, whereas the occurrence of events is usually defined by moments. Therefore, the overall trend of confidence values should be a long-term cumulative value that is driven by the influence values of key moments. However, according to the results of the survey, the three major influences on confidence are all negative. If they are modeled as lowering confidence, the longer the autonomous driving system functions, the lower the confidence must be.