Don and I use the "Easy Rider" car harness on Perry and Daisy if we are going for short rides. Although they are good once in the car, we feel they are a lot safer if we have to stop short for some reason. They hook right into the seat belt and it allows them to sit or lay down.
For trips we fold down the back seats and put them in crates for traveling any long distance.
I used to hold Daisy on my lap but those days are over when we considered the consequences of an accident.
Jackie