The Combined Effects of Impairment and Distraction on Driving
Last reviewed: 2026 · Driviology Road Safety Education Team
Quick Answer
Both impairment and distraction reduce reaction time, narrow attention, and impair judgment, and a driver affected by both at once faces a compounded risk far greater than either factor alone.
Impairment and distraction are usually discussed separately, but their effects on the brain overlap significantly, and both can be present in a single driver at once.
Shared Effects on Driving Ability
Both slow reaction time and narrow attention, even though one comes from a substance and the other from a competing task.
Why Combined Effects Are Especially Dangerous
A driver who is both impaired and distracted, for example checking a phone after drinking, faces a compounded risk that is significantly higher than either factor causes on its own.
Reducing Both at Once
Avoiding alcohol before driving and eliminating phone use are the two most effective ways to remove these compounding risks entirely.