Observers were presented with displays simulating a 3-D environment with ob
stacles in the path of motion. During the trial, observer motion decelerate
d at a constant rate and was followed by a blackout prior to the end of the
display. On some trials the rate of deceleration resulted in stopping befo
re the collision, whereas on other trials the rate of deceleration resulted
in a collision with the obstacles. The observer's task was to detect which
trials simulated an impending collision. Proportion of collision judgments
was greater for older as compared with younger observers when a collision
was not simulated. Older observers showed less sensitivity to detect collis
ions than younger observers did, particularly at high speeds. The age-depen
dent results are discussed in terms of analyses based on (tau) over dot and
constant deceleration. The results suggest that increased accident rates f
or older drivers may be due to an inability to detect collisions at high sp
eeds.