This study investigated automobile drivers' ability to localize auditory and haptic (touch) alarms in terms of speed and accuracy. Thirty-two subjects, balanced across age (20-30 years old and 60-70 years old) and gender, participated in the study. Subjects were screened for minimum hearing of 40 dB for 500 Hz through 4000 Hz auditory tones, and maximum bilateral hearing differences of 10 dB. The experiment consisted of subjects identifying the target location of an alarm while driving a 2001 Buick LeSabre at 55 mph in light traffic.

Four alarm modes were tested: 1) an auditory broadband alarm, 2) a haptic seat, 3) a combination of the haptic and the auditory alarm modes, and 4) a combination of the haptic alarm mode with a non-directional auditory alarm played from the front speakers of the vehicle. The alarms were evoked from eight target locations: the front-left, front, front-right, right, back-right, back, back-left, and left. The target locations of the auditory alarm mode existed around the interior of the car cabin using the vehicle's stock sound system speakers. The haptic alarm target locations existed in the bottom of the driver seat using an eight-by-eight grid of actuators. The experimenter evoked the alarms while subjects drove along a two-lane highway, and the alarms were not associated with any actual collision threat.

Subjects were instructed to quickly identify the location of the alarm by calling them out, while being as correct as possible. Their choice response time and target location selection was recorded. The alarms were presented approximately every minute during fifteen-minute intervals over the duration of two and a half hours. Subjects completed questionnaires regarding their preference to the alarm modes. Under the conditions investigated, subjects localized the haptic alarm mode faster and more accurately than the auditory alarm mode.

Subjects performed equally well with the haptic alarm mode and the two auditory and haptic combination alarm modes in terms of speed and accuracy in identifying their location. Subjects did express a preference for the addition of the auditory component to the haptic alarm mode, perhaps owing to a heightened sense of urgency. However, subjects preferred the haptic alarm mode on its own in response to hypothetical false alarm questions, perhaps because it was less annoying. Alarm mode discriminability was believed to affect localization accuracy and response time owing to its effect on the likelihood of correctly identifying a target location and the attention resources required to differentiate adjacent target locations.