TP 13889E
February 2002

Joanne L. Harbluk
Y. Ian Noy
Ergonomics Division
Road Safety and Motor Vehicle Regulation
Transport Canada

and
Moshe Eizenman
EL-MAR Inc.

Driver distraction and inattention are important driving safety issues. As the use of in-vehicle technologies becomes more popular, there is concern about a concomitant increase in driver distraction arising from their use. While the introduction of hands-free operation for telematics devices is intended to reduce or eliminate the distraction due to manual operation of these units, a significant proportion of the distraction associated with their use may arise not from the manual manipulation of these devices, but rather the cognitive consequences of their use.

In the present study, the impact of cognitive distraction on drivers' behavior was investigated in an on-road experiment. Twenty-one drivers drove an 8 km city route while carrying out tasks varying in cognitive complexity. Each driver drove the route under three task conditions: while performing difficult addition problems (e.g., 47+38), while performing easy addition problems (e.g., 6+9), and with no additional task. The addition questions and the participants' responses were communicated via a fully hands-free cell phone so that the participants did not have to look away from the road to manually operate the phone. Visual scanning patterns were recorded using eye tracking equipment, measures of vehicle control (braking/longitudinal deceleration) were obtained using the MicroDAS system, and drivers' subjective evaluations of workload (NASA TLX), safety and distraction were obtained through questionnaires.

An examination of drivers' visual behavior revealed that, under conditions of increased cognitive load, they made fewer saccades, spent more time looking centrally and spent less time looking to the right periphery. Less time was spent checking instruments and the rear view mirror. Many drivers changed their inspection patterns of the forward view when performing the most demanding tasks. Marked individual differences were observed in these patterns of change. Performing the additional tasks while driving resulted in more incidents of hard braking while driving. The increase in cognitive load induced by the addition questions was reflected in drivers' increased ratings of workload and distraction as well as reduced ratings of driving safety.

The results of this study indicate that even when in-vehicle devices are hands-free, significant changes in driver behaviour may result due to the cognitive distraction associated with their use. A better understanding of the ways in which drivers interact with these devices should result in improved designs that minimize the amount of distraction.

The study recommends public education, as well as continuing research to determine the need for regulating original equipment.