The Martingale does prevent escapes. It tightens around the neck which may lead to a collapsed trachea. Bichons are prone to this. So instead, we use the Easy Walk no pull harness:

http://www.petexpertise.com/dog-coll...?sef_rewrite=1

The dog can not escapee from the harness. And when he pulls (runs after a car) it will turn him around. Helps to break this bad habit.

The other thing you should do is always walk with some treats. I take a baggie with hot dog bits. When a car approaches, get the dog to focus on YOU, using the treats. If the dog does go for the car (and at the start, he will), you need to use both COME and then when you have his attention, FOCUS or Sit, so he is getting rewarded w/ the treat for doing something, NOT for chasing the car. It will take some time, and easier to train when you can use the sidewalks, but you CAN get him to stop that car chasing.

Good luck!