Never lay down to sleep in the car. Your seat belt will not work properly when bent and take your seatbelt off to lay down, you could be ejected from the car in a crash.

While it is physically possible to lie down in the backseat of a vehicle, it is extremely dangerous and illegal in almost every jurisdiction while the car is in motion. Modern vehicle safety systems, including seatbelts and airbags, are designed to protect occupants who are sitting upright and facing forward. If you are lying down, the seatbelt cannot properly restrain your body across the pelvis and shoulder; in an accident or sudden stop, you could slide under the belt (submarining) or be thrown against the interior of the car with lethal force. In 2026, many newer vehicles have "seat occupancy sensors" that will trigger persistent alarms if a weight is detected on the seat without a buckled belt. If you are a passenger in a rideshare like Uber or Lyft, lying across the seat is generally against their Community Guidelines and could result in a low rating or being banned from the platform. The only safe and legal time to lie down in a backseat is when the vehicle is safely parked in a designated rest area or campsite, preferably with the engine off to avoid carbon monoxide risks.