Traveling with your cat is never the high point in either your or their lives. Cats are such creatures of habit and most dislike a moving vehicle. As their pet guardian it is your responsibility to ensure any move across town or country will be a safe one for both of you.
Cats become very disoriented when they are I cars and many can get nauseated and start vomiting. Most will make a beeline for a safe place and that is usually under the seat or under your feet by the pedals. If you let you kitty free roam while driving you must be sure to place pillows or other barriers in the way of unsafe areas.
Kitty will likely make a dive for an enclosed place which would be under the seat or near the foot pedals. Not very safe. The rare cat can be left to free roam on a car ride. However, if you do have one of these fuzzballs be sure to block areas like the drivers foot pedals so they cannot interfere with the actual driving.
The best way to travel of course would be a cat carrier or kennel. You can even secure the carrier with a seat belt. For long drives the carrier should be very large. It is also important to get kitty used to the motion of driving. Taking her for some shorter trips around town will give you an idea of what she is like when traveling. If she does not adjust well it is time for a trip to the vet to discuss medications that will assist her with traveling. Be sure to book pet friendly hotels when you actually make your trip.
The metal crates that are used for dogs are an even better way to travel. They are large enough to fit all the essentials like food, water and a litterbox. Placing a favorite piece of cat furniture is also a comfort for kitty.
Most importantly is being sure you know where fuzzy is when you are exiting or entering the vehicle. Nothing will ruin the trip more than a kitty that gets loose.
Cat condos are great exercise for the cat. A cat towers is also great for the cat to lounge around on. Your cat deserves one right now.