How Accurate Are Pedestrians at Judging Their Own Street-Crossing Time?

Abstract

Purpose:: Crossing the street is a complicated and potentially dangerous activity of daily living. To safely cross an unsignalized street, pedestrians must judge whether or not the gap in vehicular traffic is of greater duration than the time they estimate it will take them to cross the street. Little is known however at how accurate pedestrians are in estimating the time it will take them to cross the street. The aims of this study were to compare a subject’s estimate of their street-crossing time to the time it actually took them to cross the street. This study is part of a larger project investigating street-crossing decision-making using visual and/or auditory information.

Methods:: The actual street crossing time of 13 normally-sighted subjects was measured four times by recording the time it took subjects to walk, at their usual street-crossing pace, from the curb to the other side of an unsignalized, two-lane street of one-way traffic. Subjects estimated their street crossing time four times by imaging themselves crossing the street at their usual street-crossing pace. Subjects said "start" and "stop" when they imagined themselves stepping off the curb and reaching the other side of the street respectively. The time interval between "start" and "stop" was recorded and street-crossing estimates were measured both before and after subjects actually crossed the street.

Results:: There was no significant difference between the before and after estimates of subjects’ estimated crossing times (p=0.274). There were however significant differences between subjects’ actual and estimated crossing times. This was true for both the before (p=0.0007) and after (p=0.0034) estimates.

Conclusions:: Normally-sighted subjects significantly under-estimated the time it would take them to cross an unsignalized, two-lane street of one-way traffic. On average, subjects under-estimated their crossing time by approximately 1 second and it appears that this estimate is not affected by previous experience of actually crossing that same street. These findings have important implications for street crossing safety especially for blind and visually impaired pedestrians who cannot reliably use their vision to estimate their street-crossing time.

Keywords: low vision • vision and action