Just how dangerous is driving while drowsy? According to a recent study by the Governors Highway Safety Association (GHSA), the answer may be surprising. The organization found that "a sleepy driver is just as dangerous as a drunk driver." In fact, a driver that has not slept for 24 hours is comparable to a driver operating a vehicle with a blood alcohol content of 0.10 percent. That's well over the legal limit of 0.08 percent.