If you are struggling to stay awake at the wheel, the safest first step is to stop driving. Find the nearest place where you can get completely out of traffic, park legally, and rest without exposing yourself to a different hazard. Do not wait for your destination if your attention is fading, your eyelids feel heavy, you are drifting across lane markings, or you cannot remember the last stretch of road.
NHTSA says adequate sleep is the only reliable protection against drowsy driving. Caffeine alone can leave a severely sleep-deprived driver less alert than they realize. A short nap in a safe place may improve alertness briefly, but it does not replace the sleep you need or guarantee that you are fit to continue 1.
This guide is for an adult who needs to rest in a parked car. It is not a guide to vehicle camping, long-term vehicle living, or sleeping while somebody else drives.
Choose the stopping place before you settle in
A place where parking is permitted is not automatically a place where overnight occupancy is permitted. Rules can come from local law, the road authority, posted restrictions, and the property owner. Check signs and current official information. On private property, ask the owner or manager when permission is unclear. Do not assume that every rest area, store lot, campground, or roadside turnout follows the same policy.
A safer location should let you park fully out of travel lanes and away from ramps, exposed shoulders, loading areas, moving equipment, and places where another driver may not expect a stationary vehicle. A lighted, designated rest area may be an appropriate option when it is open and local rules allow the stop 1. If your vehicle is disabled beside traffic, treat that as a roadside emergency rather than a sleeping arrangement. Call roadside assistance or emergency services and follow local instructions.
Before closing your eyes:
- Put the vehicle in park, set the parking brake, and switch the engine off.
- Check the forecast and active emergency alerts for your exact location.
- Lock the doors, but keep at least one exit clear and easy to open.
- Keep your phone accessible. If you are alone or in an isolated area, tell a trusted person where you are and when you expect to check in.
- Leave if the location feels unsafe, someone asks you to move, or conditions change.
Keep the engine off while you sleep
For an ordinary planned rest stop, switch the engine off before sleeping. Carbon monoxide is an odorless, colorless gas in vehicle exhaust. An exhaust leak can allow it to build up inside a car, and a sleeping person may be overcome before noticing symptoms 2.
Never sleep in a vehicle with its engine running in a garage or another enclosed or partly enclosed space. An open garage door does not make an attached garage safe for a running vehicle 2. Do not use a fuel-burning stove, grill, lantern, or heater inside the car.
An open window is not protection against exhaust. Before starting or driving the vehicle, make sure the tailpipe is not blocked by snow, mud, or debris. CDC warns that a snow-blocked tailpipe can allow carbon monoxide to build quickly inside the vehicle 3. If you notice an exhaust smell, a damaged exhaust system, or unexplained headache, dizziness, weakness, nausea, chest pain, or confusion, get into fresh air and seek emergency help. Do not drive yourself if you may be impaired by carbon monoxide.
Being stranded during a winter storm or another active emergency is different from choosing to stop for a nap. Contact emergency services or roadside assistance and follow instructions for your specific location and conditions. A generic engine-idling schedule is not safe advice for every vehicle or emergency.
Make sure the weather allows an engine-off rest
A parked car can become dangerously hot. Slightly opening the windows does not significantly slow the rise in temperature, and heat can threaten adults as well as children and pets 4. If the car will not remain safe with the engine off, move to a climate-controlled indoor place. Shade, a fan, or a window gap should not be treated as a heat-safety plan.
Confusion, slurred speech, loss of consciousness, seizures, very high body temperature, or hot skin with or without heavy sweating can signal heat stroke. Call emergency services and begin rapid cooling while help is on the way 5.
Cold can also become dangerous before the outdoor temperature reaches freezing. CDC notes that hypothermia can occur above 40°F when a person is chilled by rain, sweat, or cold water. Shivering, exhaustion, confusion, fumbling hands, memory loss, slurred speech, and unusual drowsiness are warning signs. Hypothermia is a medical emergency 6.
Do not plan to sleep in the car during a tornado warning. The National Weather Service says a vehicle is not a safe tornado shelter and recommends getting to the closest sturdy shelter 7. Follow evacuation orders and local alerts for flooding, wildfire, severe wind, and other hazards. If the weather makes the site unsafe, relocate before resting rather than waiting for conditions to deteriorate.
Arrange the space without creating another hazard
Once the car is securely parked and the engine is off, use the flattest supported position the vehicle allows. A rear seat or cargo area may offer more even support in some vehicles, but use it only while parked. Never lie down unrestrained while the vehicle is moving.
Move loose objects so they cannot fall onto you, and keep pedals, controls, and exits unobstructed. If you use a cover for privacy, make sure you can remove it quickly and still assess what is happening outside before opening a door. Avoid a setup that traps you behind luggage or requires you to climb over sharp or unstable objects to get out.
There is no universal rule that every sleeper should leave a window open. With the engine off, the choice depends on rain, temperature, insects, air comfort, and personal security. A small opening may help with condensation, but it does not make dangerous heat, cold, smoke, or exhaust safe. If comfortable air cannot be maintained without compromising security or weather protection, choose another place to rest.
This advice is not a substitute for supervision of children, disabled adults, or pets. Never leave them alone in a parked vehicle. Vehicle temperatures can become dangerous even on a mild day, and a slightly open window does not prevent rapid heating 4.
If alcohol, drugs, or medication are involved
Do not drive if alcohol, cannabis, another drug, or a sedating medication may impair you. NHTSA advises arranging a sober ride, taxi, rideshare, or public transportation instead of driving impaired 8.
Sleeping in the car is not a universal legal workaround. Laws differ on whether a person in a parked vehicle, in the driver's seat, or in possession of the keys may be considered in control of the vehicle. If you are impaired, arrange a safe ride or an indoor place to stay and wait for it away from moving traffic. NHTSA recommends a well-lit pickup point away from the roadway when waiting outside 9.
Reassess before you drive again
Waking up does not automatically mean you are ready to drive. Before moving the car, sit up fully and give yourself time to notice how alert you actually feel. Do not drive if you are still nodding off, repeatedly yawning, struggling to focus your eyes, losing track of your thoughts, or feeling confused. Also consider whether alcohol, drugs, medication, illness, carbon monoxide, heat, or cold could be affecting your judgment.
Check that the weather, route, and vehicle are safe, remove any window covers, return seats and cargo to a driving-safe position, and make sure every occupant can use the appropriate restraint. If you are not clearly alert and unimpaired, keep resting in a safe place, change drivers, arrange another ride, or find indoor accommodation. A deadline is not evidence that you are fit to drive.
When to get help
Call emergency services when:
- You suspect carbon monoxide exposure, especially if more than one person has headache, dizziness, nausea, weakness, chest pain, or confusion.
- Someone has signs of heat stroke or hypothermia.
- You are stranded in dangerous weather, exposed beside fast traffic, threatened by another person, or unable to leave an unsafe location.
- A person is difficult to wake, has trouble breathing, has a seizure, collapses, or seems severely confused.
The purpose of stopping is to remove the immediate risk of drowsy driving. A legal location, an engine-off setup, safe weather, and an honest check of your alertness are what determine whether resting in the car is a reasonable short-term choice.
