My dog has for the 4 years of his life ridden with me in the big truck when I'm working and rides around in the back of the dodge whether I'm just going to town or 300-1000 miles to the racetrack. He's never jumped out and enjoys riding back there 'cause he gets to smell and see the countryside. He even stays dry in the bed in a heavy rainstorm due to the way the air flows between the p/u and TT.
BTW, around here dog registration is in towns only. Since I live in the sticks, it's not required.