Many older drivers self-regulate driving behavior to be safe, so they'll avoid dangerous roads, driving in bad weather, or driving at night. I don't think you should worry about your
Our eyes change with time. The cornea, lens, and interior fluids of the eyes gradually lose their clarity, which reduces the amount of light that reaches the back of the eye. As a result, many older people find that it's difficult to see when light is low: after dark, and at dusk and dawn.
I'd recommend that your dad see his eye doctor for his regular checkup to make sure he doesn't have any new or worsening problems. Another great resource is a low-vision specialist. Low-vision specialists can recommend appropriate assistive technologies, such as special eyewear or mirrors, if appropriate, and may give your father other helpful tips to maintain his driving fitness.
dad being too cautious. This is probably an instinctive and very healthy decision.