How long is too long for a pet to be in a car?

­If you've ever been on a road trip before, you know that driving for long stretches can be exhausting. Although you're not really doing much but sitting and steering, lengthy car rides can still drain your energy. This is true for passengers and drivers alike, and­ for pets as well as humans. While the length of time a pet can endure without stopping will vary from pet to pet, especially depending on its age, there are some rules of thumb concerning the length of time that your pet can stay in a car at a stretch.

Pet experts recommend that you stop every two hours to allow your dog or cat to relieve itself and stretch its legs [source: ­BusinessWire]. Be sure to keep your dog or cat on a leash, however, to make sure it doesn't run off during one of these rest stops. You should also consider a pet microchip and always keep updated identification tags on your pet's collar. Both will help increase the chance that you'll find your pet again if it makes a break for it.

Two hours is a good rule of thumb for stopping on a long road trip, but your dog or cat can stretch that time out, especially if it's traveling in a pet carrier or crate. Your dog or cat should always be secured by a seat belt while traveling by car. There's a plethora of pet seats available that will keep your pet stable during a car ride, but a crate held in place by a seat belt is your pet's best bet for longer trips. Providing comfortable bedding and some of its favorite toys will give your dog or cat a chance to catch some slumber and keep it occupied.

If you're traveling by night, adult cats a­nd dogs sleeping in a pet crate or carrier should be able to stay in the car through the night without having to make a rest stop. This is not the same with puppies and kittens. Puppies will need to be let out once or twice during the night, no matter where you are. During the day, experts recommend that adult pets stay in a crate for no more than four hours and young pets no more than two hours [source: Woodard].

All of this assumes that you're in the car with enough air circulating to keep everyone in the car -- includi­ng your pet -- comfortable. It's a whole different ballgame when the car is parked and you leave your pet behind. Leaving your dog or cat alone in a car -- even with its windows cracked -- can be dangerous. On a sunny, 80 degree Fahrenheit day (26.6 degrees Celsius), the interior of a parked car can reach 105 degrees Fahrenheit (40.5 degrees Celsius) within 10 minutes [source: PFD]. You should never leave your pet in the car alone for more than a minute or two, especially when the weather is hot.

To avoid situations that force you to leave your pet in the car, include your pet in your vacation planning. There are many Web sites dedicated to pet-friendly travel and destinations. By spending a little time before you leave finding places that will welcome your dog or cat, you won't have to find out the hard way just how long is too long for your pet to be in the car.

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