The visual ability of two drivers may be about the same during the daylight hours and be markedly different at night. Driving safely at night requires seeing well not only under low illumination, it also requires one to see low contrast objects. Someone wearing dark clothes and crossing the street in front of the driver is much harder to detect at night than during the day because there is much less contrast at night between darkly clothed pedestrians and a dark background. Glare resistance is the extent to which the driver can still see critical objects and events while facing a steady source of glare such as the setting sun or the light from the headlights on a steady stream of oncoming traffic at night. Glare recovery is the rapidity with which the driver's vision functioning returns to what it was before the glare was encountered.
Eye movements impaired by one or more vision conditions can result in visual scanning deficiencies.
There could also be a tendency to look at a specific object too long or continuously look straight ahead. Consequently, the driver may fail to react to hazards and fail to heed traffic signs and signals. Changing lanes could be especially hazardous if the driver spends an excessive amount of time looking to the rear of the vehicle. Visual perception impaired by one or more vision conditions can result in difficulties with performing several visual tasks at the same time.