When my boys are bickering while I drive, My oldest daughter let out a scream "Shuuutt uuuuupp!!" enough for boys to shut up. She's always a boss over the boys. When I had an issue with my son, I asked my daughter to take care of it for me. She's good to keep boy shut.
If my daughter not with me. Sometime I pulled over and tell them shut up and be quiet. Then I pull out and drive. If boys don't behave, I slammed the brake and pulled over hard and snarled at them to tell them knock it off. They went silent and not to mess with Daddy for long time till we get home.
Catty