According to USA Today, adjusting the temperature as needed, sleeping in the backseat and utilizing the resources that are available allows travelers to sleep comfortably in a car. Cleaning the car and packing blankets beforehand makes sleeping comfortably in a car possible.
USA Today recommends spreading blankets or a sleeping bag in the backseat to make the car more comfortable. Blankets are not completely necessary, however. A warm sweater or jacket also protects against cold weather. Running the heater on full power for a few minutes before sleeping heats the interior of the car for up to several hours. During warm weather, sleep with the doors locked and the windows slightly open to allow fresh air inside if the car becomes too warm.
USA Today recommends placing a tarp over the car if it is parked in a public space. The tarp should be positioned to cover the windows for privacy. If possible, find a place where it is legal to sleep in the car. Campgrounds, trail heads and some 24-hour discount store parking lots are places that allow people to legally sleep in their car. National Geographic advises travelers to bring or purchase plenty of water when sleeping in a car, particularly during warmer weather.
The Department of Motor Vehicles advises all travelers to have a well-stocked emergency kit in the car at all times. The items in the kit can be used to remain comfortable in the car in the case of a flat tire or other emergency situation that requires waiting for assistance.