Yes with a muzzle. A little dog can usually get away without, but medium size or above can't if the driver is ok. Larger dogs are sometimes ok, but carry a muzzle in case.
I just noticed that your doggy's a pup still. This means you probably won't have to worry about the muzzle for a little while. They're usually OK but it's a bit of a lottery whether or not the driver's a dog lover.