Using Virtual Environments to Assess Time-to-Contact Judgments from Pedestrian Viewpoints

This paper describes the use of desktop and immersive virtual environments to study judgments that pedestrians make when deciding to cross a street. In particular, we assess the ability of people to discriminate and estimate time-to-contact (TTC) for approaching vehicles under a variety of conditions. Four experiments observing TTC judgments under various conditions are described. We examine the effect of type of vehicle, viewpoint, presentation mode, and TTC value on TTC judgments. We find no significant effect of type of vehicle or of viewpoint, extending prior work to cover all views typically encountered by pedestrians. Discrimination of short values for TTC judgments is generally consistent with the literature, but performance degrades significantly for long TTC values. Finally, we find no significant difference between judgments made in a desktop environment versus a head-mounted display, indicating that tracking the approaching vehicle with one's head does not aid discrimination. In general, people appear to use strategies similar to those that pedestrians use to make real-world, street-crossing decisions.