STUDY OF DRIVER DISTRACTION DUE TO VOICE INTERACTION. IN: HUMAN FACTORS IN DRIVING, SEATING AND VISION

This paper describes tests that were carried out during the development of a new telematics service to determine its potential influence on drivers' mental distraction. The service combines text-to-speech (TTS) technology with the communication function of a cellular phone. With this service, drivers operate their in-vehicle information system by simple voice commands, download news and information from a portal site to the system via a cellular phone, and have the information read to them by the TTS synthesizer. Tests were conducted with a driving simulator and an actual vehicle, with participation by twenty subjects. Both the driving simulator and actual vehicle were equipped with steering wheel buttons and an instrument panel light emitting diode (LED) that illuminated at random intervals during the driving tests. The subjects were instructed to follow a preceding vehicle and to press the steering wheel button when the LED illuminated. In addition, they were also given a simultaneous information device task such as listening to a prerecorded radio broadcast or news read aloud by the TTS synthesizer, viewing the navigation display or talking on a cellular phone. Their response time to the illumination of the LED was measured under these conditions. Vehicle data were also recorded to determine the amount of lateral lane displacement and change in the headway distance that occurred at the time the information device tasks were performed. The indexes were then compared for the different information device tasks assigned. The results showed that the mental distraction level when listening to a TTS reading of information was comparable to that of listening to the car radio. The use of TTS technology should not have an appreciable effect on driving behavior. The vehicle's lateral lane displacement and secondary task response time were found to be effective test techniques for estimating the mental workload.