The answer might just be "no."

The functions of augmented reality head-up displays (AR-HUDs) have become popular as they display digital images on windshields in order to alert drivers to, for example, possible collisions and smartphone activity.

It might be cool to have one in your car but not safe, according to experts at the University of Toronto.

Professor Ian Spence at the university's Department of Psychology, together with his two students Yuechuan Sun and Sijing Wu, did two tests to be able to measure the impact of AR-HUDs on driving.

Spence calls AR-HUDs "added visual information" and studied what happens when there are two souces of visual information in just one visual field.

In the experiment, participants underwent a test to measure their visual fields, by counting and reporting a number of spots arranged on a computer screen. The spots would randomly appear and the goal was to report the number of spots as quickly and as accurately as possible.

The researchers also deliberately included one black-outlined square in one of the series of trails and called the square a "secondary stimulus." This secondary stimulus would unpredictably appear, and the researchers wanted to see whether or not this was noticeable to the participants.

Results of the tests showed that when the square did not appear, accuracy was high. However, when the square appeared with a number of spots, it was missed at an average of about one in 15 times.

The researchers then raised the number of spots and, in doing so, the rate also rose to one in 10 times, and accuracy lowered. Spence's team then concluded that a primary stimulus takes much of the attention of a participant. It becomes more difficult to attend to a secondary stimulus. Moreover, when the primary stimulus becomes increasingly demanding, the primary and secondary stimuli interfere with each other.

"Drivers need to divide their attention to deal with this added visual information," said Spence.

With AR-HUDs, drivers would have to divide their attention between what is on the road in front of them and what may appear on their windshields, also in front of them.

In a second test, the participants were asked to identify shapes as they randomly appeared along with the spots: a triangle, square or diamond. Most of the time, the shapes were either missed or misidentified.

Spence stresses that when the driving environment becomes demanding, the attention of the driver is competed for by a number of stimuli.

"Missed warnings and slowed reaction times present real threats to safety," he explained.

The team's research was funded by a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada. Findings about the division of visual attention are published in the online journal PLOS ONE.

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