Speech Tactons Improve Speech Warnings for Drivers

Abstract

This paper describes two experiments evaluating a set of speech and tactile driver warnings. Six speech messages of three urgency levels were designed, along with their tactile equivalents, Speech Tactons. These new tactile warnings retained the rhythm of speech and used different levels of roughness and intensity to convey urgency. The perceived urgency, annoyance and alerting effectiveness of these warnings were evaluated. Results showed that bimodal (audio and tactile) warnings were rated as more urgent, more annoying and more effective compared to unimodal ones (audio or tactile). Perceived urgency and alerting effectiveness decreased along with the designed urgency, while perceived annoyance was lowest for warnings of medium designed urgency. In the tactile modality, ratings varied less as compared to the audio and audiotactile modalities. Roughness decreased and intensity increased ratings for Speech Tactons in all the measures used. Finally, Speech Tactons produced acceptable recognition accuracy when tested without their speech counterparts. These results demonstrate the utility of Speech Tactons as a new form of tactile alert while driving, especially when synchronized with speech.

Language-based multimodal displays for the handover of control in autonomous cars

“…before L M and "Notice!" before L L , since this has shown to provide distinctively different urgency ratings in previous studies [1,6,16]. Finally, in L H the handover was enforced, since imminent actions would be needed in such critical situations, while in L M and L L , the handover was only requested.…”

“…They then evaluated the warnings in the presence of a critical driving event and found lower reaction times [14]. The use of Speech Tactons, tactile cues modelled on the structure of speech, was found to improve the recognition of warnings' urgency and perceived effectiveness [16]. Finally, comparing a set of language-based messages to abstract ones, they found similar performance as well as a slight improvement of driving metrics when using language-based cues [17].…”

“…We used three different Levels of Designed Urgency (LDU) for the envisioned situations (Level High -L H , Level Medium -L M and Level Low -L L ), as in previous studies [16,17]. We also used situations where either the car would hand over control to the driver (CD) or the driver to the car (DC).…”

Priming Drivers before Handover in Semi-Autonomous Cars

“…Second, we did not test voice-based commands despite their potential (e.g. [30,42,44]). Finally, our drivers were not able to turn off the pre-alert, whereas this might be a relevant option in real cars, for example, to signal to the car that you noticed the pre-alert.…”

Thermal in-car interaction for navigation

“…According to the Multiple Resources Theory [9] information should be distributed across modalities not occupied by the primary task. Using haptic feedback, especially in combination with different feedback types, has been shown to decrease reaction time whilst not increasing mental demand [5] in a car. Most commonly used non-visual feedback types are auditory and vibrotactile.…”