"Direct and indirect impacts of the COVID-19 pandemic on operational conduct of pediatric vaccine clinical trials".

The coronavirus 2019 (COVID-19) pandemic, as well as the resulting public health measures, impacted many aspects of society. The conduct of important pediatric vaccine trials was among these. Analyzing data from six ongoing non-COVID-19 pediatric vaccine trials we aimed to assess the operational impact of the COVID-19 pandemic using descriptive analyses. We identified multiple operational disruptions in trial conduct. Additionally, we identified higher percentages of missed routine vaccinations than investigational vaccines throughout the observation period. Overall, the impact of the COVID-19 pandemic was most apparent early in the pandemic period while adaptations to the pandemic were developed; however, some disruptions persisted throughout the observation period. Pediatric vaccine clinical trials are critical to developing new and/or improved vaccines for the pediatric population. Continued evaluation of the impacts of COVID-19 on pediatric vaccine clinical trials is warranted.

Assessing subjective criticality of take-over situations: Validation of two rating scales.

Assessing subjective criticality of take-over situations is crucial for understanding of take-over behavior and comparing studies. However, no validated rating scales exist that assess subjective criticality of take-over situations. In a driving simulator study, two rating scales, the Scale of Criticality Assessment of driving situations from Neukum et al. (2008) and the Criticality Rating Scale, were tested on their validity to assess the subjective criticality of take-over situations. Besides, the subjective and behavioral changes over the repeated experience of take-over situations were investigated. Twenty-five participants experienced a set of five take-over situations with varying time-to-collisions (TTC) at the moment of the take-over request, twice. After each of the first five take-over situations, participants rated the criticality on one scale, after each of the second five situations on the other scale. Correlation coefficients between TTCs and criticality ratings for each scale were calculated. Also, the changes of subjective and behavioral measures over the trials were investigated. Correlation coefficients indicated a strong correlation between criticality ratings and TTCs. Hence, both scales are equally valid for the assessment of the criticality of take-over situations. The repeated experience of the take-over situations did not affect effort ratings, take-over times, or steering wheel positions. But brake input decreased with increasing practice, indicating a safer take-over behavior. Hence, results of studies with repeated experience of take-over situations are relatively valid as only brake behavior changed with increasing practice.

What happens when drivers of automated vehicles take over control in critical brake situations?

Even with automated vehicles, driving situations with short time headways and extreme vehicle dynamics may arise when unpredictable events occur. If drivers take back control under such conditions, it is uncertain how they behave and how well they can cope with the situation. This issue has not been investigated yet and is subject to our study. In a driving simulator, non-distracted participants (N = 42) experienced nine critical situations caused by a braking vehicle in front of them. Time headway and longitudinal vehicle dynamics were varied to create different degrees of objective criticality. Participants' criticality ratings, take-over behavior, and driving performance were recorded and analyzed. The results indicate that participants were sensitive to changes in objective criticality and adapted their behavior. Take-over times were very fast under all conditions and participants showed higher criticality ratings, more intense decelerations, and more lane changes with increasing objective criticality. To avoid a collision, participants decelerated much more than the automation and changed lanes, even though this was not necessary. Thereby, they raised the risk of vehicle instability, rear-end collisions, and collisions with overtaking vehicles. To conclude, take-overs in critical brake situations may be a threat to the safety of drivers and other road users because drivers' reactions are more pronounced than necessary. These results suggest that assistive functions are required to support drivers in critical take-over situations.

Behavioral Changes to Repeated Takeovers in Highly Automated Driving: Effects of the Takeover-Request Design and the Nondriving-Related Task Modality.

OBJECTIVE: We investigated drivers' behavior and subjective experience when repeatedly taking over their vehicles' control depending on the design of the takeover request (TOR) and the modality of the nondriving-related task (NDRT). BACKGROUND: Previous research has shown that taking over vehicle control after highly automated driving provides several problems for drivers. There is evidence that the TOR design and the NDRT modality may influence takeover behavior and that driver behavior changes with more experience. METHOD: Forty participants were requested to resume control of their simulated vehicle six times. The TOR design (auditory or visual-auditory) and the NDRT modality (auditory or visual) were varied. Drivers' takeover behavior, gaze patterns, and subjective workload were recorded and analyzed. RESULTS: Results suggest that drivers change their behavior to the repeated experience of takeover situations. An auditory TOR leads to safer takeover behavior than a visual-auditory TOR. And with an auditory TOR, the takeover behavior improves with experience. Engaging in the visually demanding NDRT leads to fewer gazes on the road than the auditory NDRT. Participants' fixation duration on the road decreased over the three takeovers with the visually demanding NDRT. CONCLUSIONS: The results imply that (a) drivers change their behavior to repeated takeovers, (b) auditory TOR designs might be preferable over visual-auditory TOR designs, and (c) auditory demanding NDRTs allow drivers to focus more on the driving scene. APPLICATION: The results of the present study can be used to design TORs and determine allowed NDRTs in highly automated driving.