You could also try a remote shock collar.
It does have an option to control how harshly it shocks your pet. If you do go for this option, click the button on the remote when your dog takes off for the car. Next option which is more time consuming. It's another shock collar, but you install the wires inside the ground around the border of your yard. If you don't like this shocking idea, you can do one of those rope walkers. That you tie between two trees and you attach your dog to it. It's like a leash. I'm not sure what the official name for it is, so it might sound quite odd.
