In addition, the driver's glance behaviour was analysed as an indicator of how much they would interrupt the NDRT and monitor the vehicle automation.
Due to the NDRT it was not possible to reliably assess gaze behaviour by eye tracking since the magazine covered a significant portion of the necessary field of view of the remote cameras.
The level of interference with the NDRT associated with processing the HMI outputs was analysed using a [chi square]2-test on the frequency of behavioural observations in the two HMI conditions.
Interference with NDRT: Observations and Monitoring Ratio.
We investigated whether additional speech output would facilitate human-automation cooperation by effectively informing the driver about upcoming automated driving manoeuvres and would, therefore, cause less interference with the execution of a NDRT. It may be precisely the possibility of engaging in NDRTs without the need of interruptions that would make automated driving useful and attractive.
There was no difference in the frequency of observed interruptions of the NDRT between the "speech + generic" and "generic" condition.
As the participants were engaged in a primary visual NDRT, speech output may have particularly facilitated processing the visually presented HMI.
Furthermore, the rating procedure used to determine the level of interference with the NDRT could possibly be improved.
The NDRT measures reading comprehension, reading vocabulary and reading rate.
A reading test such as the NDRT could be administered, for example, to students when they first enroll in Accounting I.