The legality of sleeping on the side of the road varies wildly by country and local jurisdiction. In the United States, most states prohibit sleeping in your car on the shoulder of a highway or interstate for safety reasons; however, many allow "resting" at designated Rest Areas for a specific number of hours (typically 2 to 8 hours). In the UK and much of Europe, it is generally legal to sleep in your car if you are "correctly parked" in a designated lay-by or parking area, provided you aren't causing an obstruction or violating local "no overnight camping" bylaws. A critical legal trap exists regarding alcohol: in many places, including the UK and several U.S. states, being inside a vehicle with your keys while intoxicated—even if you are asleep in the back seat with the engine off—can lead to a "Drunk in Charge" or DUI charge. For maximum safety and legality, it is always better to seek out designated truck stops, 24-hour service stations, or retailers like Walmart (where permitted) rather than the side of a road, where you risk being hit by traffic or moved along by police.