Use of adaptive cruise control functions on motorways and urban roads: Changes over time in an on-road study

The interaction between perceived safety and perceived usefulness in automated parking as a result of safety distance

Improved safety and traffic efficiency are among the proclaimed benefits of automated driving functions. In many scenarios, traffic safety and efficiency can be somewhat contradictory, especially in the perception of a user. In order for potential users to accept the automated system, it is necessary to find the optimal system configuration. Therefore, it is important to understand how the factors underlying acceptance develop and interact. In this study, seven safety distances of an automated parking system were implemented resulting in parking manoeuvres of varying efficiency (in terms of required moves). Participants experienced each configuration twice and rated their perceived safety and perceived usefulness. The results show that maximizing safety distances results in high perceived safety, yet also a diminished perceived usefulness due to reduced efficiency. On the other hand, maximum efficiency leads to a lower perceived safety and thus, a reduced rating of perceived usefulness. Furthermore, in some participants, perceived safety increased gradually, while for others, a threshold effect could be observed. The results demonstrate that the specification of a sole system characteristic can have multiple effects. These have to be considered to maximize acceptance.

Effects of nine typical technologies for primary autonomous vehicles on road safety in China

The autonomous vehicle is profoundly changing the future of transportation safety. The reduction in collisions with different injury degrees and the savings of crash-related economic costs if nine autonomous vehicle technologies were promoted to be wildly available in China are evaluated. The quantitative analysis was divided into three main parts: (1) Calculate the technical effectiveness of nine autonomous vehicle technologies in collisions through a systematic literature review; (2) Apply the technical effectiveness to estimate the potential effects on avoiding collisions and saving crash-related economic costs in China if all vehicles had these technologies; and (3) Quantify the influence of current technical limitations in speed applicability, weather applicability, light applicability, and active rate on potential effects. Definitely, these technologies have different safety benefits in different countries. The framework developed and technical effectiveness calculated in this study can be applied to evaluate the safety impact of these technologies in other countries.

Quantitatively mining and distinguishing situational discomfort grading patterns of drivers from car-following data

Situational discomfort awareness plays an important role in decision making among drivers and has rarely been discussed in detail in previous research. An instrumented vehicle was used to collect car-following data from multiple drivers, thereby quantitatively examining situational discomfort grading patterns using a new discomfort grading method and the latent Dirichlet allocation model. In this process, the gas pedal data and speed difference data are particularly involved in the computation for providing broader meaning to discomfort and building more comprehensive situations. The results show that individual discomfort awareness varies between drivers. More importantly, the potential patterns of situational discomfort grading are extracted, which provides knowledge for characterizing drivers in the context of discomfort awareness. The knowledge achieved can be further applied to distinguish drivers and identify the typical comfort and discomfort zones. This study has great value for promoting investigations on traffic psychology and developing more effective and customized driver assistant systems.

Effects of platooning on signal-detection performance, workload, and stress: A driving simulator study

Platooning, whereby automated vehicles travel closely together in a group, is attractive in terms of safety and efficiency. However, concerns exist about the psychological state of the platooning driver, who is exempted from direct control, yet remains responsible for monitoring the outside environment to detect potential threats. By means of a driving simulator experiment, we investigated the effects on recorded and self-reported measures of workload and stress for three task-instruction conditions: (1) No Task, in which participants had to monitor the road, (2) Voluntary Task, in which participants could do whatever they wanted, and (3) Detection Task, in which participants had to detect red cars. Twenty-two participants performed three 40-min runs in a constant-speed platoon, one condition per run in counterbalanced order. Contrary to some classic literature suggesting that humans are poor monitors, in the Detection Task condition participants attained a high mean detection rate (94.7%) and a low mean false alarm rate (0.8%). Results of the Dundee Stress State Questionnaire indicated that automated platooning was less distressing in the Voluntary Task than in the Detection Task and No Task conditions. In terms of heart rate variability, the Voluntary Task condition yielded a lower power in the low-frequency range relative to the high-frequency range (LF/HF ratio) than the Detection Task condition. Moreover, a strong time-on-task effect was found, whereby the mean heart rate dropped from the first to the third run. In conclusion, participants are able to remain attentive for a prolonged platooning drive, and the type of monitoring task has effects on the driver's psychological state.