Abstract: In this study two experiments were conducted to investigate factors affecting timeto contact judgment. The results showed that : When the rate of dilation of the opticalcontour of the moying object was constant (d / dt = 0), (1) The main time--perceptualinformation was distance, velocity and acceleration. In some way, visual informationPlayed a certain role in the judgment of bine to contact. Time--perceptual cues used tocontrol action were usually the results of combination of Physical information andvisUal information. (2) Time judgment showed significant gender effect men providedhigher and more accurate judgment than did women. (3) When the object moved inconstant velocity, a linear model was used to fit the dare obtained in TTC judgmentwhich could describe the relation between actual TTC and judged TTC.

Key words: bine to contact perception visual information physical information