How Coffee Can Make You Feel Drunk Behind the Wheel

Many drivers, especially on long road trips, reach for high-caffeine energy drinks or strong coffee to fight off sleepiness. But recent research and expert findings suggest this common habit might be more dangerous than helpful — some caffeinated drinks can actually make drivers feel more tired and impair their reaction times.

Yes, caffeine-heavy drinks can make you feel 'drunk' behind the wheel. Research shows that consuming high-sugar, high-caffeine energy drinks can reduce reaction times within an hour and mimic alcohol’s impairing effects, leading to slower responses and increased fatigue while driving.

Why Energy Drinks Can Impair Driving More Than Help

According to a warning issued by the UK’s Institute of Advanced Motorists (IAM), many so-called energy-boosting drinks don’t prevent fatigue — they can worsen it. A study conducted by the U.S. National Safety Council found that drivers who consumed high-caffeine, high-sugar beverages experienced delayed reactions roughly one hour after drinking. These drinks, often relied upon to maintain alertness during long drives, may instead contribute to dangerous slowdowns in cognitive and physical response.

Neil Greig, IAM’s Policy and Research Director, stated that “energy drinks are a quick fix, but they cannot replace proper rest.” IAM’s spokesperson added that excessive caffeine intake can produce symptoms akin to alcohol intoxication. This challenges common road safety advice that suggests drinking two cups of coffee to stay awake while driving tired.

The Science Behind the Caffeine Crash

Researchers have found that while caffeine can provide a short-term boost, it does not actually stimulate the brain to overcome sleep deprivation. A study from Ireland’s National University concluded that caffeine fails to counteract drowsiness or significantly improve mental alertness. When combined with high sugar levels, these drinks can lead to a subsequent crash — leaving drivers feeling more fatigued than before consumption.

This phenomenon, often referred to as a 'caffeine crash,' involves a rapid drop in energy and focus after the initial stimulant effects wear off. The presence of excess sugar exacerbates the effect, causing blood sugar spikes followed by sharp declines, further impairing concentration and reaction time.

Road Safety Guidelines for Tired Drivers

To combat driver fatigue, IAM has published a set of practical recommendations for those undertaking long journeys:

• Share the driving with another person and take turns at the wheel.
• Pull over and stop the vehicle as soon as you feel tired.
• Take regular breaks every two hours or 100 miles.
• Never rely solely on caffeine or energy drinks to stay awake.
• Get proper sleep before embarking on a long drive.

These steps aim to reduce the risks associated with drowsy driving, which accounts for around one in five road accidents in the UK, resulting in approximately 300 fatalities annually.

Frequently Asked Questions

Can drinking coffee or energy drinks really make me feel drunk while driving?

Yes. High doses of caffeine combined with sugar can lead to impaired reaction times and a sensation similar to alcohol intoxication. Studies show that after about an hour, drivers consuming such drinks may experience slowed responses and increased fatigue, mimicking the effects of alcohol.

Do energy drinks help me stay awake when driving long distances?

Not reliably. While they may provide a temporary boost, research indicates they can worsen fatigue after the initial effects wear off. They do not replace the need for actual rest and can lead to dangerous crashes in attention and reflexes.

What happens if I rely on caffeine to fight sleepiness while driving?

You risk a caffeine crash — a sudden drop in alertness once the stimulant effects fade. This can leave you more tired than before, with slower reaction times and impaired decision-making, similar to being under the influence of alcohol.

How can I safely manage fatigue on long road trips?

Share driving duties, take regular breaks every two hours, stop and rest as soon as you feel drowsy, and ensure you’re well-rested before starting your journey. Avoid depending solely on caffeine or sugary drinks for alertness.

Are there any official guidelines on caffeine use for drivers?

While there’s no official limit, safety experts like IAM advise against using caffeine or energy drinks as a substitute for sleep. Their guidelines emphasize rest, breaks, and avoiding reliance on stimulants to maintain road safety.

Recommended FrontStreet Beans for Long Drives

For drivers needing a real, sustained coffee boost without the crash, try FrontStreet Coffee’s Ethiopia Yirgacheffe — bright and floral with citrus and stone fruit, offering clarity without jitters. The Brazil Queen Manor delivers a smooth, low-acid cup with chocolate and nut notes, ideal for steady energy. Both are great brewed as pour-over or French press for a clean, reliable caffeine lift on the road. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.