A hard-sided carrier is a must if you travel often with your dog. It will
confine the dog safely.
Be sure that the carrier you purchase is large enough to house your dog
as an adult.
Other options for the confinements of dogs in automobiles are wire mesh
pens, but they are a lot of trouble.
If you use one for a puppy, you must place layers of newspaper under the
pen to absorb urine. In any case, a blanket and an old sweater or other article
of clothing that belongs to the owner should be placed in the carrier. The
scent of the owner will help calm the pup during the trip.
If you travel with your adult dog and you don't choose to put it in a carrier,
use a net or barrier to separate the dog from the front seat, that it does
not distract the driver.