As you're traveling the highways and byways, make sure you know which areas have better gas prices. (Getty Images)

There's nothing quite like a long road trip. Long sunny days, roadside attractions, unusual stops, long lost friends ... it all adds up to a slice of American life that many travelers romanticize.

As wonderful as a road trip can be, there are a lot of expenses involved that quickly add up to a whole lot of money. Eating at an endless stream of restaurants adds up fast. Gas adds up, too. Finding hotel rooms gets expensive. A road trip starts off like a fun adventure but can often end up with a big bill.

Here are some strategies for keeping costs low on a road trip.

Choose Grocery Stores

It can be tempting to stop at various roadside restaurants for food on a road trip, but the cost of doing so will add up quickly. A much better approach is to shop at grocery stores for your food supplies and keep them in your trunk.

The items you need for simple meals, such as bread, sandwich toppings, fruits and finger foods, are less expensive than restaurant meals. They're also convenient, as they're always in the car whenever you feel hungry. You can eat in the car or stop at any nice roadside park or rest stop that strikes your fancy.

Bring a Cooler

A cooler enables you to keep some food cold in the car, which means that you can easily keep items such as sandwich toppings, condiments and beverages, cold as you're traveling. You'll need to refill it with ice regularly, but ice is available at virtually every gas station and grocery store in America.

Know Which States Have Cheaper Gas

As you're traveling the highways and byways, make sure you know which areas have better gas prices and which have more expensive fuel. In general, southern states, particularly the mid-south and the southeast, have the lowest prices on gas, but there are extreme variations from state to state. You should also fuel up when leaving the Great Plains and heading into the Rocky Mountains.

Use the app GasBuddy to figure out where the cheapest fuel is near you and pay careful attention as you approach the border of a state. It can often be worthwhile to fuel up before leaving a state, even if you're not low on gas. For example, going from New Mexico to Arizona sees an increase of about 22 cents per gallon of gas, according to AAA. Filling up before you cross can easily save you several bucks, and if you're aware of such shifts throughout your trip, the savings can add up.

Camp Overnight

Rather than staying at a hotel, which would be super expensive, or sleeping in your car, which is uncomfortable and offers no way to bathe, consider camping during your trip. Borrow a tent if you don't have one and pop it in your trunk along with sleeping bags and pillows and camp at campgrounds along the way.

Most campgrounds designed for car camping have a shower house that will give you a place to take a shower, brush your teeth and wash your face. A reasonably sized tent gives you plenty of space to stretch out while sleeping. Best of all, the whole package is pretty cheap. Most tent camping sites are inexpensive and non-electric sites, which have no electric hookup available, are even more so.

This works even better if you pack appropriately. Make sure you're bringing a towel and a washcloth, and if it's a long road trip, bring along some quarters, as many campgrounds have a washing machines and dryers for cleaning your clothes.

Bring Friends

The easiest way to keep a road trip cost low is to have more people with whom you can split costs. A passenger reduces the cost of fuel by almost half, lodging by half and food by a notable amount. A second passenger cuts costs even more. Plus, having people join you adds a social element to the road trip that can make things even more enjoyable.