Purpose

To examine how road users with different degree of hearing loss experience safety and mobility in transport situations, compared to road users with normal hearing.

Methods

A questionnaire study was conducted with participants recruited from the local branch of The Swedish hard of hearing society. A normal hearing control group, matched on age, gender and geographical location, was selected from a commercial database. The response rate was 35 % (n = 194) in the group with Hearing Loss (HL) and 42 % (n = 125) in the group with Normal Hearing (NH). The individuals with hearing loss were grouped into four groups according to the degree of their hearing loss (mild, moderate, severe and profound).

Results

Hearing loss affected some specific aspects regarding transport situations, while others remained unaffected. Individuals with hearing loss were not as likely to have a driving license, but for those who have, hearing loss had no effect on mileage per year. Loss of hearing had an effect on criteria for choosing mode of transportation, but in the aggregate, no difference between the groups could be shown in the distribution of how much each mode of transportation was used. With a few exceptions, hearing loss did not affect the ratings of importance of hearing for different transportation modes. Hearing loss affected most questions regarding hearing and driver abilities, while avoidance of specific traffic situations was not associated with hearing loss. Hearing loss had only minor effects on the factors causing inattention when driving, and on the interest in a warning system for driver inattention. The interest in a warning system for driver inattention was high regardless of hearing category.

Conclusions

Hearing loss influences the prevalence of driving license and criteria for choosing mode of transportation, however has no effect on the distribution of how much each mode of transportation was used. In general, in this study, respondents with higher degree of hearing loss were less concerned about the effect of hearing loss, indicating that they might be using coping strategies. The interest in warning system for inattention and the attitude towards strengthening of auditory information in traffic situations is high regardless of hearing category. This suggests further research on coping strategies and on design of support systems accessible for drivers with hearing loss.

Purpose

To compare the effect of cognitive workload in individuals with and without hearing loss, respectively, in driving situations with varying degree of complexity.

Methods

24 participants with moderate hearing loss (HL) and 24 with normal hearing (NH) experienced three different driving conditions: Baseline driving; Critical events with a need to act fast; and a Parked car event with the possibility to adapt the workload to the situation. Additionally, a Secondary task (observation and recalling of 4 visually displayed letters) was present during the drive, with two levels of difficulty in terms of load on the phonological loop. A tactile signal, presented by means of a vibration in the seat, was used to announce the Secondary task and thereby simultaneously evaluated in terms of effectiveness when calling for driver attention. Objective driver behavior measures (M and SD of driving speed, M and SD of lateral position, time to line crossing) were accompanied by subjective ratings during and after the test drive.

Results

HL had no effect on driving behavior at Baseline driving, where no events occurred. Both during Secondary task and at the Parked car event HL was associated with decreased mean driving speed compared to baseline driving. The effect of HL on the Secondary task performance, both at Baseline driving and at the lower Difficulty Level at Critical events, was more skipped letters and fewer correctly recalled letters. At Critical events, task difficulty affected participants with HL more. Participants were generally positive to use vibrations in the seat as a means for announcing the Secondary task.

Conclusions

Differences in terms of driving behavior and task performance related to HL appear when the driving complexity exceeds Baseline driving either in the driving task, Secondary task or a combination of both. This leads to a more cautious driving behavior with a decreased mean driving speed and less focus on the Secondary task, which could be a way of compensating for the increasing driving complexity. Seat vibration was found to be a feasible way to alert drivers with or without HL.

Purpose

To examine eye tracking data and compare visual behavior in individuals with normal hearing (NH) and with moderate hearing loss (HL) during two types of driving conditions: normal driving and driving while performing a secondary task.

Methods

24 participants with HL and 24 with NH were exposed to normal driving and to driving with a secondary task (observation and recall of 4 visually displayed letters). Eye movement behavior was assessed during normal driving by the following performance indicators: number of glances away from the road; mean duration of glances away from the road; maximum duration of glances away from the road; and percentage of time looking at the road. During driving with the secondary task, eye movement data were assessed in terms of number of glances to the secondary task display, mean duration of glances to the secondary task display, and maximum duration of glances to the secondary task display. The secondary task performance was assessed as well, counting the number of correct letters, the number of skipped letters, and the number of correct letters ignoring order.

Results

While driving with the secondary task, drivers with HL looked twice as often in the rear-view mirror than during normal driving and twice as often as drivers with NH regardless of condition. During secondary task, the HL group looked away from the road more frequently but for shorter durations than the NH group. Drivers with HL had fewer correct letters and more skipped letters than drivers with NH.

Conclusions

Differences in visual behavior between drivers with NH and with HL are bound to the driving condition. Driving with a secondary task, drivers with HL spend as much time looking away from the road as drivers with NH, however with more frequent and shorter glances away. Secondary task performance is lower for the HL group, suggesting this group is less willing to perform this task. The results also indicate that drivers with HL use fewer but more focused glances away than drivers with NH, they also perform a visual scan of the surrounding traffic environment before looking away towards the secondary task display.

An on-road study was conducted to evaluate a complementary tactile navigation signal on driving behaviour and eye movements for drivers with hearing loss (HL) compared to drivers with normal hearing (NH). 32 participants (16 HL and16 NH) performed two preprogrammed navigation tasks. In one, participants received only visual information, while the other also included a vibration in the seat to guide them in the correct direction. SMI glasses were used for eye tracking,recording the point of gaze within the scene. Analysis was performed on predefined regions. A questionnaire examined participant's experience of the navigation systems. Hearing loss was associated with lower speed, higher satisfaction with the tactile signal and more glances in the rear view mirror. Additionally, tactile support led to less time spent viewing the navigation display.