When we started traveling over 10 years ago we had a dog and 2 cats. They logged 68,000 miles with us and everyone behaved well enough and we all had a good time.
Those 3 are now passed on and a new cat has joined our journeying even though we don't travel as much. A week ago we added a puppy so these 2 will join us for more miles. We would not and do not leave home without them.
Strange place, new sounds, dogs can become unsettled. Our dog used to bark sometimes so we closed the shades, windows, curtains, made sure the AC was on to make background noise and turned on the radio. It worked...we often checked by making it sound and look like we left but walked back to make sure he was quiet...and he was. But each pet is different. Some traveling folks don't realize that a dog that is quiet and calm at home can become upset when traveling. Its a challenge everyone needs to find a solution to.