Nah, it will cause more trouble. Although it made a little sense at first, further logical thinking made it useless.

Let's say you have a powerful magnet, so powerful that it can repel other cars. By using real magnet, try facing the same pole to each other, it will repel but if more force is applied, the magnetic repulsive force will be useless. On highway, car can travel up to 100km/h. Do some simple calculations and you will get the force and energy generated.

If your magnet is not powerful, the same thing will happen. If it is powerful, it can repel the car and the car will crash into other objects that are non-metallic, which is not feasible.

That's one of the point.