The Effects of Lead Time of Take-Over Request and Nondriving Tasks on Taking-Over Control of Automated Vehicles

Abstract

Automated vehicles have received great attention, since they offer the possibility of significantly increasing traffic safety, mobility, and driver comfort. Current automation technology is still imperfect; therefore, there will still be situations in which the automation will not be able to handle and will request the driver to suspend nondriving tasks and take over control of the automated vehicle in a limited period of time. Accordingly, it is necessary to understand the effects of the lead time of take-over request as well as nondriving tasks on driver take-over. The present driving simulator experiment studied the effects of lead time and various realistic nondriving tasks on take-over behavior and driver acceptance to the automated vehicle. Results suggested optimal driver take-over performance when the lead time of the take-over request was 10–60 s for general nondriving tasks. Specifically, a take-over request with lead time at 10–60 s led to lower crash rate, greater minimum time-to-collision, and lower lateral acceleration. However, a longer lead time (e.g., 15–60 s) was necessary to achieve optimal driver acceptance even though drivers could successfully take over control with shorter lead time (e.g., 10 s). In addition, driver take over performance was significantly influenced by nondriving tasks. When more sensory modalities were occupied or when the cognitive load was very low, driver take-over performance was impaired, especially when the take-over request was too late (e.g., lead time was 3 s). Potential applications of the results in designing of take-over request in automated vehicles were further discussed.