Arrival-time judgments on multi-lane streets: the failure to ignore irrelevant traffic

How do road users decide whether or not they have enough time to cross a multiplelane
street with multiple approaching vehicles? Temporal judgments have been investigated
for single cars approaching an intersection, however, close to nothing is known about how
street crossing decisions are being made when several vehicles are simultaneously
approaching in two adjacent lanes. This task is relatively common in urban environments. We
report two simulator experiments in which drivers had to judge whether it would be safe to
initiate street crossing in such cases. Matching traffic gaps (i.e., the temporal separation
between two consecutive vehicles) were presented either with cars approaching on a single
lane or with cars approaching on two adjacent lanes, either from the same side (Experiment 1)
or from the opposite sides (Experiment 2). The stimuli were designed such that only the
shortest gap was decision-relevant. The results showed that when the two gaps were in sight
simultaneously (Experiment 1), street-crossing decisions were also influenced by the
decision-irrelevant longer gap. Observers were more willing to cross the street when they had
access to information about the irrelevant gap. However, when the two gaps could not be seen
simultaneously but only sequentially (Experiment 2), only the shorter and relevant gap
influenced the street-crossing decisions. The results are discussed within the framework of
perceptual averaging processes, and practical implications for road safety are presented.