"It was concluded that sleep deprivation has a greater impact on driving performance than a BrAC of 22 μg/100mls of breath, as measured by driving simulation. Coffee is not an effective countermeasure for sleep deprived driving and drivers’ ability to judge this impairment is suggested to be limited."
You are underestimating the impact of sleep deprivation, and the ability for a person to recognize the impacts while sleep deprived.
https://bmcpublichealth.biomedcentral.com/articles/10.1186/s...
"It was concluded that sleep deprivation has a greater impact on driving performance than a BrAC of 22 μg/100mls of breath, as measured by driving simulation. Coffee is not an effective countermeasure for sleep deprived driving and drivers’ ability to judge this impairment is suggested to be limited."