Many of the major U.S. car rental agencies allow dogs to travel in their cars, with the universal proviso being that a cleaning fee will be charged if the car interior has been soiled or covered in dog hair. (Thrifty, Payless, Enterprise, Dollar and E-Z Rent-A-Car apparently do not have company pet policies — you’ll need to check with the office providing the car to see if dogs are allowed.)

Six agencies include a pet policy on their websites:

Hertz and Advantage: “Domestic pets are allowed in Hertz vehicles (excessive pet hair or soiling caused by animals will result in an extra cleaning charge).” The link leads you to Hertz’s FAQs; you’ll need to scroll down to Question #177. Advantage has the same policy.

National and Alamo (“Help,” in both sites’ menu bars, will take you to a FAQ page, where you’ll need to type “pet” in the search bar): “Yes, domesticated pets are allowed to travel in vehicles. Excessive pet hair, soiling or damage caused by animals may result in extra charges.”

Avis: “Avis does not have a strict pet policy, but please be sure to return your rental car in clean condition and free of pet hair, etc. to avoid cleaning fees.” [10/6/13 Please note, however, Jeff’s comment below, and my response — in view of his report, I suggest checking with the local Avis office you’re actually renting from to see if they are, in fact, strict about pets. And if your pup isn’t traveling inside a carrier or crate, I’d pack a seat protector, or a sheet or towel you can drape over the passenger area. Just before we return our rental cars, we go over the back seat with a lint roller to pick up the hairs that inevitably escape even Chloe’s PetTube; I suggest also carrying a pack of Windex wipes for nose prints on the windows.]

Budget: “Housebroken pets are invited to travel in your rental car, just as they do in your personal car. Although Budget doesn’t assess an extra fee for pets, pet owners will incur an additional charge for any damage caused by animals, or any special cleaning required as a result of shedding or accidents.” The link leads you to Budget’s “Common Questions;” look under “Reserving a Car” (“Rates”).

If you’re traveling with a small dog, it’s pretty easy to keep your rental car clean — either have your dog travel in a travel seat or carrier, or bring an old sheet or towel and cover the backseat with it. If you think your dog might throw up, a picnic blanket (with both a soft side and a water-resistant back side) will do a better job of protecting the seat. Here’s an example, available on Amazon: Waterproof Picnic Blanket. If your dog is in heat, consider having her wear dog diapers, available at Petco or PetSmart. I also suggest bringing a packet of Windex Wipes, so you can quickly clean nose prints off the inside of the passenger windows before you turn your car in.