Shared Zones and Autism Spectrum Disorder

Background: Shared zones present an alternative means of calming traffic whilst promoting active travel, and social civic engagement. Shared zones are characterized by the removal of markers traditionally delineating the road and footpath. They are regulated by basic traffic rules with design features encouraging informal social interactions between users to promote safe behaviours. Safe negotiation of a shared zone relies on an individual’s ability to rapidly scan, assess and respond to ambiguous social stimuli. This ability may be impacted by impairments in cognitive processing, such as autism spectrum disorders (ASD), potentially compromising the safety of vulnerable users. There is a paucity of research examining the impact of shared zones on the visual scanning patterns of pedestrians with and without social difficulties.

Objectives:  To compare the visual scanning patterns of pedestrians with and without ASD when crossing a shared zone, benchmarked against traditionally marked pedestrian crossings (zebra crossings).

Methods: Head-mounted eye-trackers were used to record participants’ eye movements as they completed a series of crossings across in a shared zone and a zebra crossing. Eye movements were measured as number of fixations, fixation duration and location relative to predetermined areas of interest (AOI). AOIs were categorised as traffic relevant and not-traffic relevant. The eye movements of 40 adult pedestrians, 19 with ASD and 21 typically developing, were successfully recorded.

Results: A total of 3,287 fixations were analysed. The eye tracking data revealed that all pedestrians were less likely to look at traffic relevant objects in the shared zone (47.1%) compared to the zebra crossing (59.1%). There was no between group difference in relation to fixations on traffic relevant versus not traffic relevant objects between pedestrians with ASD and the control group. Pedestrians with ASD did, however, have 16msec shorter median fixation durations overall compared to the control group (p<0.001). The total number of fixations with eye contact were miniscule across both groups, showing no difference between the groups, neither in the shared zone, nor at the zebra crossing.

Conclusions: It has been proposed that shared zones increase the attention and care taken by users. However, both groups fixated more on traffic relevant objects at a zebra crossing suggesting that zebra crossings cue pedestrians to attend to traffic relevant objects to a higher degree than a shared zone regardless of impairments in cognitive processing. The clear lack of difference in visual scan patterns between the groups indicated that participants with ASD were no more at risk in the shared zone than pedestrians without ASD. Observed between group differences in fixation durations, with pedestrians with ASD exhibiting shorter fixation durations overall, suggest that those with ASD processed visual stimuli more rapidly or inadequately in comparison to their typically developed peers. This finding requires further investigation. Finally, the few fixations that could be classified as eye contact across both groups, potentially challenge the idea that shared zones increase social interaction between road users.