Why can fitness to drive be impaired even by just a small quantity of alcohol?

Even a small amount of alcohol impairs fitness to drive because it reduces the field of vision and diminishes spatial vision. This means your ability to see objects on the sides and judge distances is weakened, which is crucial for safe driving. While reaction time may also be affected by alcohol, the key early impairments are in vision, making it harder to notice hazards and react appropriately. This is why even low alcohol levels can significantly increase the risk of accidents.