While most seniors are capable, conscientious drivers, some have experienced age-related declines in the skills that support safe driving, thus pose a hazard to themselves and to other road users. There seems to be agreement that older adults should stop driving when their skills have declined to the point that they pose a risk to themselves and others, but there are few guidelines to aid older drivers or their families in determining when one should no longer drive. This study was designed to identify driving behaviors and non-driving measures that predict hazardous driving errors such as leaving the roadway or hitting pedestrians other cars. Ten younger and 30 older adults participated in the study; older participants were divided into three groups of 10 based on performance on cognitive screening tests. Participants completed tests of attention, working memory, spatial memory and timing ability as well as simulated driving scenarios. The younger participants made significantly fewer hazardous errors than did the older drivers with poorer cognitive performance. Driving behaviors associated with increased hazardous errors in older participants included poor maintenance of lane position in low complexity condition and making abrupt lane changes when complexity increased. Poor performance on a measure of working memory and on an anticipation timing task were also associated with increased hazardous errors in the older participants. / Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Psychology / "December 2005."