Sleeping/Napping in Your Car Safely

If you’re feeling sleepy while driving, it is a good idea to pull over and decide how best to proceed. Can you get a ride from family, friends or a rideshare/taxi? Are you due for your medication, in which case you could safely drive again once it kicks in? Or is a nap your best option? (Note that it is important to discuss any sleepiness while driving with your doctor, so they can help optimize your treatment plan and help assess your fitness to drive.) Or you may not be driving at all but just need a private/quiet/etc. space for a nap and have no better alternative. Many people with hypersomnias need to nap in their cars occasionally and have to decide where to park and how to protect themselves while they sleep.

Another consideration is the risk of someone seeing you and calling the police. Unfortunately, it is difficult to determine whether someone sleeping in a car is napping, inebriated, in medical distress or homeless and living in a vehicle. If an observer calls the police, the officers will wake you and assess the situation. This can be a terrifying experience and occasionally lead to serious legal consequences.

While there will always be some risks to napping in your car, knowing the relevant laws and implementing strategies for setting up a sleeping area in your car will help you to avoid problems. Continuing to drive while extremely sleepy is very risky. Knowing when and how to nap in your car is important to help protect you and others from the significant harm of a car accident.

Is It Legal?

In the U.S., laws on sleeping in a car vary by state. In addition, some municipalities have passed laws specific to sleeping in a car that are stricter than state law. The best way to determine the law in your area is to do an Internet search on “(your state/province name) law on sleeping in a car”. If you are in a major city, it is also a good idea to search on “(city name) law on sleeping in a car”.

Some states do allow sleeping in a rest area. There may be restrictions on overnight stays. Look for posted signs stating whether sleeping is prohibited or restricted to certain times.

There are a number of national chain businesses that allow trucks, RVs, and cars to park overnight, including Walmart, Cabela’s, Cracker Barrel, Lowe’s, and Home Depot. It is best to check ahead of time by calling and asking the manager if it is ok to sleep in your vehicle on their site. This 2020 CNN article explains that the number of store sites allowing overnight RV parking has declined in recent years for some of these businesses.

If a rest area with lenient state laws or one of the businesses mentioned above is not available, you are taking a chance pulling over to sleep anywhere else. Parking on the side of a busy road is very dangerous and should be avoided. Experienced car travelers recommend church parking lots, casino parking lots and quiet residential streets as the best places to sleep without being bothered. If you select one of these options, always be aware that you and your car will be on either public or privately-owned land and subject to a visit by authorities.

How to Minimize Risk in an Encounter With Police/Security and Passersby

If you know you will be sleeping in a car in a specific place for a certain time, you may want to let the local authorities know in advance. For example, if you nap in your car during lunch hour at work, let the security guards know you’re all right and to keep an eye out for your safety. If you are at an event with a security presence (like campus security at a college graduation, or parking attendants at a state fair) and intend to take a car nap, give them a heads up and your plate number.

  • Windshield sun reflectors, tinted windows or window shades can all be used to keep passersby from viewing the interior of the car. As an added benefit, these tools may help with light and temperature control.
  • Make a sign to keep in the car that an observer will see if they notice you sleeping. Either a rearview mirror tag or dashboard sign with the words “Napping” or “Napping for driving safety” will let passersby and police know that you are not inebriated or in medical distress. If you have a handicapped placard, hang it up. The signs probably won’t stop the police from waking you, but it may reduce their suspicion that you are breaking vagrancy or DUI laws.
  • A small pillow and sleeping mask will not only make your nap more comfortable, but they also immediately communicate to passersby and police that you are intentionally napping and not in distress or inebriated. Napping in a passenger seat also communicates that the nap is intentional and that you haven’t fallen asleep at the wheel. Some of these visual cues may look a little corny, but they can help reduce the tension of police officers as they approach an unknown vehicle and driver.
  • Lock the car doors so the police (or anyone else) cannot touch you or enter the car.
  • Carry a medical alert card with you. You may be very groggy and unable to respond clearly when awakened by the police. One strategy for addressing this situation is to carry a medical alert card with you, or even put extra cards in cars that you drive. It may also be a good idea to request and carry with you a brief signed letter from your doctor. When pulling over for a nap, take out your driver license, your medical alert card (and your letter) and put them on the seat beside you (face down) before you fall asleep. The Hypersomnia Foundation website has a free idiopathic hypersomnia medical alert card for you to download and print out. You may also want to provide a template letter to your doctor for their modification on their letterhead, such as:
    • To Whom It May Concern:
      My patient, [name], has idiopathic hypersomnia, a neurologic sleep disorder. Their condition requires frequent naps. Your empathy and understanding is greatly appreciated.
  • If you are awakened by the police, try to remember to keep your hands visible by placing them on the steering wheel or dashboard. When the officer requests identification or an explanation for why you are sleeping, tell the officers that your ID and medical alert card (and letter) are on the seat beside you and ask if you may reach for them.

For a more detailed discussion on your rights when you are pulled over or approached by police while in a car, the American Civil Liberties Union (ACLU) provides advice and information on their website. Drivesafeonline also provides some helpful advice. If you believe that you are at high risk of encountering the police while napping in your car, knowing your rights and how to react during the encounter may help you avoid serious legal consequences.

Is It Safe to Run the Heat or Air Conditioning?

It is true that thousands of people (including taxi and long-haul truck drivers) sit or sleep in cars for hours every day with the engine idling so that the heat or air conditioning system can keep the interior air comfortable. It is also true that every year some people die from carbon monoxide generated by their vehicle. Carbon monoxide is a clear, odorless gas produced by internal combustion engines. Under certain circumstances, it can accumulate imperceptibly within the vehicle, leading to suffocation and death. Recent, accurate data specifically on accidental carbon monoxide poisoning in vehicles is not available, but sporadic news stories confirm that even with modern vehicle technology, on rare occasions people are poisoned by their car.

Carbon Monoxide Poisoning Symptoms

With a little pre-planning, you may be able to sleep comfortably in your car without running the HVAC system. In cold weather, blankets or a sleeping bag may provide enough warmth. In hot weather, you may need to crack open your windows, but it is only safe to do so if you are not idling the vehicle.

If it is too hot or cold for these methods to work, you will have to run your HVAC system in order to sleep. While the risk of carbon monoxide poisoning from an idling gas vehicle can never be zero, there are concrete steps you can take to greatly reduce the risk:

  • The type of vehicle matters. Electric vehicles typically have zero carbon monoxide emissions. Although hybrid vehicles may emit carbon monoxide when they use their gas engines, it is usually at much lower levels than all gas vehicles, and hybrids usually do not emit when idling. For hybrid vehicles, it may be prudent to confirm your particular vehicle’s carbon monoxide output during idling.
  • Check your car’s exhaust system before you take a trip to make sure it’s working properly. Have it inspected annually to make sure no exhaust is leaving the system and leaking into the car cabin. An emissions test is critical to ensuring that the carbon monoxide concentration is being reduced to proper levels before exiting the exhaust system. Holes in the floor or trunk of the vehicle must be repaired so the passenger cabin is protected from exhaust.
  • Choose a parking spot with maximum airflow around the car to allow exhaust to dissipate. Avoid garages or enclosed spaces; choose open-air lots instead. The idea is for the exhaust to blow away from the car instead of getting pulled into the cabin by the heat or air conditioning system.
  • Make sure the exhaust pipes are not blocked by snow or mud.
  • Do not sleep or ride in a truck bed or under a canopy, because it is not sealed from exhaust like the cabin. Do not sleep with open windows or hatches with the vehicle idling, which allows the exhaust a direct path into the cabin.
  • Keep a battery-operated carbon monoxide detector in your car. Since you can’t see or smell carbon monoxide, a detector is a great way to ensure that levels in your car are safe.

For more information on the topic of carbon monoxide poisoning in vehicles, we recommend this article by Jeremy Laukkonen at Lifewire.com.

Because most idling vehicles generate pollution, some states and municipalities have passed anti-idling legislation that determines how many minutes drivers may idle their engines in specific locations. These laws and enforcement activities target primarily trucks, buses and commercial vehicles, but a few laws include passenger vehicles. For more information, read this article by Amy Leibrock at SustainableAmerica.org.

In summary, choose the safest location, let people know you are there if possible, and give every indication that you are napping. 

Vetted by Our Medical Advisory Board. Revised 2/2021.