When you’re on a road trip, rest stops are conveniently located across the country. But despite their name, rest stops get slightly complicated when you actually want to rest. If you’re on a long trip or RV vacation and need to find a parking spot, you’d better check ahead. Because, in some cases, staying at a rest stop overnight is illegal.

States that prohibit parking overnight at a rest stop

If you’re in any of the following states, you can’t park your car or RV at a rest stop overnight: Alabama, California, Colorado, Connecticut, Deleware, Florida, Georgia, Illinois, Indiana, Kentucky, Maine, Maryland, Massachusetts, Nebraska, New Hampshire, New York, North Carolina, Ohio, Pennsylvania, South Carolina, South Dakota, Tennessee, Vermont, Virginia, and Wisconson.

That’s half of the US states that prohibit staying at a rest stop overnight. In fact, each state has its own guides to how long you can stay. You can read about them on Interstate Areas, which spells out each state’s policy.

States that allow parking overnight at a rest stop under certain conditions

So those are the 25 states you can’t stay overnight at, which leaves all the other states. But don’t get your hopes up, because some of these states still have strict limits on how long you can actually stay at a rest stop. In general, most states allow you to rest for 10 hours. Washington is a notable exception, which allows overnight parking for only eight hours.

Then there’s the holy trinity of rest stop states: Nevada, New Mexico, and Texas. Not only do these three states allow overnight parking, but they’ll let you stay for 24 whole hours. In theory, you could spend a whole day at these rest stops, snacking on vending machine food and using their bathrooms.

But whether you’re able to stay overnight or not, rest stops are open 24/7. That means, if you need to pop into one, you’re more than welcome to. But if you can’t stay overnight, here are some things you should know.

If you can’t park overnight, how long can you stay?

If you’re getting weary-eyed on the road, many experts suggest taking a 15-20 minute nap. It’ll be enough to keep you going for the next 50 or so miles until you need another nap (or, if you’re an efficient sleeper, maybe 20 minutes is all you need). And every rest stop in America will allow you to stay for that long.

The lowest time limit for staying at a rest stop is two hours. Thankfully, there are only two states with that low of a time frame: Pennsylvania and Tennessee. The most common standard for non-overnight states is four hours, which is held by Deleware, Kentucky, Michigan, Minnesota, New Hampshire, North Dakota, and South Dakota. And some states are right in the middle, at a three-hour limit, such as Florida, Illinois, Maryland, New York, and Ohio.

Other states don’t have a posted time limit, even if you can’t stay overnight. So use common sense while traveling. And do your research to see what the rules are in the state you’re traveling through.