Although poor visibility, which is exacerbated by age-related changes in vision, is a leading contributor to fatal nighttime crashes, there has been little research on the extent to which drivers recognize and compensate for their visual limitations at night. This study investigates the effects of drivers' age and low light on speed, lane keeping, and visual recognition of typical roadway stimuli. Young, middle-aged, and elderly participants drove on a closed road course in day and night conditions at a "comfortable" speed without speedometer information. During night tests, headlight intensity was varied over a range of 1.5 log units using neutral density filters. Results showed that average speed and recognition of road signs decreased significantly as functions of increased age and reduced illumination. Participants of all age groups failed to compensate fully for diminished visual recognition abilities in low light; however, older drivers behaved more cautiously than the younger participants. Lane keeping showed nonlinear effects of lighting, which interacted with task conditions and drivers' lateral bias, indicating that older drivers drove more cautiously in low light. Recognition of pedestrians at night was significantly enhanced by retroreflective markings of limb joints as compared with markings of the torso, and this benefit was greater for middle-aged and older drivers.
Abstract