Background  

The Pulfrich stereoillusion occurs spontaneously in diseases inducing asymmetric visual pathway delays. Its influence on driving performance has never been investigated and was, therefore, assessed using a three-dimensional (3D) computer driving simulation.

Methods  

A 3D driving scenery of a road with obstacles was visualised on an autostereoscopic 3D display. Seven normal subjects drove at a speed of 6 m/s using a steering wheel and three angles of view of the scenery (0°, 45° to left, and 90° to left) with different interocular delays (25 ms on the right, 25 ms on the left, and no delay). One subject drove the scenery at an angle of 90° without delay and with a delay of 8 ms, 16 ms, and 25 ms on the right and left, respectively, at speeds of 6 m/s,12 m/s and 18 m/s.

Results  

Stereoillusion only influenced car position if the angle of view was 90° (p<0.05). At this angle, increasing car speeds were associated with larger car displacements (delay on rightp<0.001, on leftp<0.01) and smaller delays with smaller car displacements (p<0.001).

Conclusions  

This study showed that Pulfrich phenomenon has an influence on car position only if the viewing angle is 90°. No influence could be found if the driving direction corresponded to the visual axis of the driver. These findings are in agreement with reports of patients with spontaneous Pulfrich phenomenon who indicate that while driving, distances are only misjudged when looking sideways.