Sleep researchers at the University of Britain at Loughborough did several tests on fatigued drivers to compare the effects of different methods for a driver can use to stay awake. They put the volunteers in driving simulators while they were sleepy and let them drive. Some of the tests included rolling down windows for cold exposure, blasting the radio and slapping oneself in the face to try to stay awake. But what researchers found worked the best was a Caffeine Nap.
The Caffeine Nap is simple: you drink a cup of coffee and immediately take a 15-20 minute nap. Researchers found coffee helps clear your system of adenosine, a chemical which makes you sleepy. The combination of a cup of coffee with an immediate nap chaser provided the most alertness for the longest period of time in tests. The recommendation was to nap only 15 minutes, no more or less and you must sleep immediately after the coffee.
Most adult Americans drink coffee, and caffeine is possibly the most widely used and longest self-administered drug in mankind. Caffeine is a stimulant and is often used when people want to stay awake. The caffeine nap is an example of the paradoxical effect of many substances in the body.
A Stanford University test publshed in 2010 found that caffeine during the day disrupts night sleep more in morning people (larks) than in evening people (owls).