Napping in your car safely

if you have idiopathic hypersomnia or narcolepsy type 1 or 2

Many people with hypersomnias (PWH) need to sleep or nap in their cars, whether they are taking a break from driving or just need a private, quiet, temperature-controlled space for a nap and have no better option. Here are some tips on how to plan ahead so you can do it legally and more safely.

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What should I do if I’m sleepy while driving?

If you’re feeling sleepy while driving, you should pull over to a safe place and decide what to do:

  • Can you get a ride from family, friends, or a rideshare service or taxi? 
  • Are you due for medicine that would allow you to safely drive again once it kicks in? 
  • Or is a nap in your car the best option? 

Never park on the side of a busy road to decide what to do or to sleep – this is very dangerous. Pull into a parking space or parking lot while you consider what to do next.

Always discuss any sleepiness while driving with your doctor, so they can adjust your treatment plan and help assess your fitness to drive.

Where can I legally sleep in my car?

In the U.S., there are various state and local laws on sleeping in cars. The best way to know 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, also search “(city name) law on sleeping in a car.” 
  • Look for posted signs stating if sleeping is banned or restricted to certain times.
  • Be aware of anti-idling laws. To learn more, read this article at SustainableAmerica.org.

If you might need to nap in your car, research the best options on your route ahead of time, which tend to be:   

  • Rest areas: Some states allow sleeping at rest areas. However, there may be limits on overnight stays, which are usually posted on signs. 
  • National chain businesses: A few national chain businesses allow trucks, RVs, and cars to park overnight. Yet, according to this 2020 CNN article, there may be fewer sites over time. Call and ask the store manager. Some of these businesses include: 
    • Walmart
    • Cabela’s
    • Cracker Barrel
    • Lowe’s
    • Home Depot

If these aren’t an option, experienced travelers recommend:

  • Church parking lots
  • Casino parking lots
  • Quiet residential streets

To learn more, visit these web pages:

How can I limit problems with police, security, and passersby?

A woman wearing a neck pillow sleeps sitting up under a blanket in the back seat of a car

  • Tell the authorities in advance if possible. For example, if you nap in your car during your lunch hour at work, let the security guards know your license plate number, that you’re all right, and to keep an eye out for your safety.
  • Use windshield sun reflectors, tinted windows, or window shades to keep passersby from seeing in your car. These may also help with light and temperature control.
  • Make a sign to keep in your car with the words “napping” or “napping for driving safety.” You can hang the sign from your rearview mirror or put it on your dashboard. If you have a handicapped permit, show that too.
  • Use a small pillow and sleeping mask, and nap in a passenger seat. This will make your nap more comfortable and tell passersby and police that you’re sleeping on purpose.
  • Lock the car doors so no one can enter your car while you’re sleeping.
  • Prepare before you fall asleep, because you may be groggy and unable to respond clearly if awakened by the police. Put your driver’s license and vehicle registration on the seat beside you (face down).
  • If you’re awakened by the police:
    • Keep your hands visible by placing them on the steering wheel or dashboard.
    • If the officer requests ID, tell them it’s on the seat beside you and ask if you may reach for it.
    • If the officer asks why you’re sleeping, you do not need to disclose your medical condition. You can simply say that you’re napping for driving safety.

If you believe you’re at high risk of a police encounter while napping in your car, knowing your rights and how to react may help you avoid serious legal problems. To learn more, visit:

Is it safe to run the heat or air conditioning while napping in my car?

Yes, but only if you’re very careful to avoid exposure to carbon monoxide (a clear, odorless gas found in vehicle exhaust), which can get inside your vehicle and lead to suffocation and death. 

Here are the symptoms of carbon monoxide poisoning:

Icons that show a stick figure experiencing these symptoms: headaches, nausea, dizziness, breathlessness, collapse, and loss of consciousness
Icons that show a stick figure experiencing these symptoms: headaches, nausea, dizziness, breathlessness, collapse, and loss of consciousness

If you’re asleep when the carbon monoxide symptoms begin, they’re unlikely to wake you up so you can get out of the car. 

On chilly days, extra outerwear, blankets, and sleeping bags may help you sleep comfortably without using the car’s heat. When the temperature inside the car is too hot, there’s a risk of heat stroke or death. Consumer Reports tests showed that even on a partly cloudy day when the outside temperature is 61 degrees F, the temperature inside the car can rise to 105 degrees F in 1 hour. If the temperature inside your vehicle is unsafe or so uncomfortable that you cannot fall asleep, then you’ll need to run the heat or air conditioning while napping.

How can I avoid carbon monoxide poisoning if I have to run my car’s heat or air conditioning while sleeping?

  • Keep a battery-operated carbon monoxide detector in your car. You can’t see or smell carbon monoxide, so a detector can alert you if the level in your car becomes unsafe.
  • When possible, choose an electric or hybrid vehicle.
    • Electric vehicles usually don’t emit any carbon monoxide.
    • Some hybrid vehicles emit carbon monoxide while idling, although usually at much lower levels than all-gas vehicles.
    • Gas vehicles emit the most carbon monoxide while idling.
  • Have your car’s exhaust system inspected yearly to make sure no exhaust is leaking into your car’s interior.
    • Get a regular emissions test to make sure the carbon monoxide concentration is low enough before leaving the exhaust system.
    • Fix any holes in the floor or trunk so your car’s interior is protected from exhaust.
  • Choose a parking spot with a lot of airflow to lower exhaust exposure. Choose open air lots, and avoid garages or enclosed spaces. 
  • Make sure your exhaust pipes aren’t blocked by snow, mud, or anything else.
  • Don’t sleep with open windows or hatches or in a truck bed (with or without a canopy) because this increases your exposure to exhaust.

Published Feb. 12, 2021 |
Revised Jan. 24, 2024
Complete update Sep. 15, 2023 |
Approved by our medical advisory board