What is highlighted as a key factor for driver fitness in AR 600-55?

Physical and mental fitness standards are emphasized in AR 600-55 as crucial for driver fitness. These standards ensure that drivers possess not only the necessary physical capabilities, such as vision, coordination, and reflexes but also the mental acuity required to make quick decisions while driving. The regulation recognizes that impaired physical or mental health can significantly affect driving performance, leading to accidents and operational hazards. Thus, a driver's ability to safely operate a vehicle is directly linked to their overall fitness, making it a fundamental requirement in ensuring road safety within the Army.