Tiredness can affect your mind and ability to drive in a slew of ways, too, so there’s no one way in which an accident will happen. According to Susan Miller, a lead researcher and certified sleep expert at SleepMattressHQ.com, being sleepy can impair your judgment and decision-making, reduce awareness of your surroundings (from cars to road conditions to traffic signals), and affect your coordination, balance and fine motor skills.

“Even a momentary lapse of attention can be dangerous while driving, so prioritizing safety is important,” she added.

Jeff Kahn, a sleep expert and the CEO and co-founder of Rise Science, agreed. “Microsleeps, in particular, are a cause for alarm, as they can last only a few seconds and occur unknowingly,” he said. “While this might not seem like much, on a highway traveling at 65 miles per hour, those seconds can mean the difference between life and death.”

Further, the dangers of driving while sleepy are often compared to the dangers of driving drunk. Kahn said 24 hours worth of sleep deprivation — at once, or accumulated over time — results in the same cognitive impairment equivalent as a blood alcohol content (BAC) of 0.10%, which is higher than the legal limit. And again, he added, it’s unsafe to drive even before you reach that point.

He pointed to the concept of “sleep debt,” or not getting enough sleep cumulatively. “If you regularly miss an hour of sleep for 10 consecutive nights, your cognitive impairment can be as severe as if you hadn’t slept for 24 hours straight,” he explained.

When Drowsy Driving Is Most Likely To Occur

One of the two time ranges when this occurs may surprise you. According to the Department of Health of New York State, most sleep-related crashes occur between 1 p.m. and 4 p.m., and 2 a.m. and 6 a.m. So yes, driving in the early morning isn’t a great idea, but that “afternoon slump” period isn’t either.

This is when bodies are typically the most tired. “Importantly, these are the times when you’re biologically-inclined to be more drowsy, thanks to the peaks and dips of your circadian rhythm (your internal body clock),” Kahn said. “Your circadian energy dips will happen regardless if you had enough sleep or not, but sleep deprivation will make you feel drowsier at these times than you otherwise would.”

Unfortunately, many factors can contribute to this, though some may be more common than others. Here are a few of the most common ones:

Not getting enough solid sleep on your vacation

“One of the biggest contributors to drowsy driving is sleep deprivation,” Miller said. “This can lead to difficulty concentrating, slower reaction times and even falling asleep at the wheel.”

While the amount of sleep each person needs will vary, most adults need seven to nine hours a night, she added. (BTW, “junk sleep,” or low-quality sleep, doesn’t count.)

A sleep disorder

A bigger sleeping issue may be going on, so checking with a doctor is smart. “Some disorders, like obstructive sleep apnea, cause low-quality sleep as sleep is often interrupted or restricted, thus low-quality and less restorative,” said Nicole Eichelberger, a sleep expert at Mattressive.

What’s even scarier is that it’s not always noticeable. “Unfortunately, most people who suffer from sleep disorders are unaware,” she continued. “Therefore, it is essential to seek medical help if you notice excessive daytime sleepiness.”

Medications or alcohol

Miller also listed alcohol and medications, such as antihistamines or benzodiazepines, as contributors to drowsiness and impaired cognitive function. So if you’re enjoying a few cocktails by the pool, for example, be cognizant of this.

“Even small amounts of alcohol and certain drugs can cause drowsiness, poor coordination and slower reaction times, making driving dangerous,” she said. To avoid this, Eichelberger urged reading the side effects listed on the medicines you take, and to avoid driving if drowsiness is listed.

When and how long you’re driving

The time of day and distance matter, too. Many of us road trip to our vacation destinations and often power through the drive in order to get there or get home.

“Driving overnight (which can be tempting to avoid traffic) increases the risk of experiencing sleepiness, even if you think you are well-rested,” said Holly Milling, a clinical psychologist, behavioral sleep medicine specialist and director of The Sleep Practice. “Driving for long periods of time, at any time of day, is also tiring, and driving without a break can increase vulnerability to sleepiness.”

Signs You Should Pull Over Immediately

Simply put, you shouldn’t drive while sleepy, even if you think you can make yourself stay awake. More specifically, here are some other danger signs these experts listed:

• Being unable to remember driving for the last few minutes

• Struggling to focus your eyes and concentrate

• Drifting into another lane

• Head bobbing

• Yawning

• Feeling easily frustrated

• Rubbing your eyes or struggling to keep them open

• Following cars too closely

• Getting restless or fidgeting

• Not keeping a consistent speed

• Braking too late

• Missing signs and exits

“Even if you don’t feel like you’ll fall asleep, these signs indicate that your driving ability is impaired and that it’s unsafe to continue driving,” Kahn said.

What To Do If You’re Tired At The Wheel

As tempting as it sounds, the answer isn’t louder music, colder air or talking to someone. “The only cure for sleepiness is sleep,” Milling said.

Take a short nap

While napping in public may feel uncomfortable, it’s crucial. You can take a nap at a rest area, gas station or other place you feel safe. And hey, only a short nap is needed.

“Ideally, you should take a 20 to 30 minute nap to feel refreshed, but not so long that you enter a deep sleep cycle and wake up feeling groggy,” Miller said. “If you’re unable to nap, simply resting your eyes or having a break from driving for a few minutes can also be helpful.”

Add some caffeine to the mix

While caffeine can help, Miller continued, it’s a short-term fix and it can’t cure severe fatigue. She recommends drinking about 200mg of caffeine (equivalent to a cup of coffee) 30 minutes before getting back on the road.

Having a coffee between napping and driving also adds time between waking up and driving, which Kahn said is important. He encourages having that buffer time “to ensure the post-nap grogginess doesn’t affect your driving skills (even if you’ve only napped for less than 20 minutes).”

Combining the two can eliminate mid-afternoon sleepiness for up to an hour, according to a study in the journal Psychophysiology. But again, these experts say a nap comes first and foremost. “Whether you include caffeine or not, though, the most important ingredient is the nap,” Milling emphasized. “Never skip sleep in favor of a double espresso.”

Exercise

Lastly, while it may seem counterintuitive, some movement (along with the nap) can help. “A short burst of exercise can wake you up and increase your alertness,” Miller said. She encouraged light stretching or a short walk. You could even get some errands done during this time, like walking around the grocery store.

Consider other options that will get you home safely

If these options feel undoable or aren’t cutting it, don’t let that deter you. “Call someone to drive you home or the rest of the way,” Eichelberger urged. “You can also find a motel [and] rest for the night, or get a cab and head home.” While a Lyft ride or motel stay won’t be inexpensive, it is cheaper — and safer — than the alternative.

Long-term, Eichelberger recommended maintaining good sleep habits. If you notice excessive fatigue often, she added, consider talking to a sleep doctor so you can avoid car accidents (and various other problems).

Being proactive is always smart, too. Milling mentioned not driving if you’ve been awake for 18+ hours and scheduling breaks every couple of hours, to start. This way, you’re less likely to get caught in a drowsy driving situation.

While vacations and life can keep us busy, sacrificing sleep isn’t a great idea — especially if you’re ever behind the wheel.This article originally appeared on HuffPost.