Smoking may be banned in cars 

I agree with the idea "smoking  should be banned in cars" because it is not good for human beings' health,especially for kids under 18. Also, smoking does not set a good example for the children in the car, because it is a proven unhealthy habit that can lead to future sickness. Smoking can damage your child's health, even if they are not smoking, because they're inhaling your second hand smoke.
Smoking in the car environment has many hazards. For example, it may lead to blindess. Passengers in the back also smoking may cause the driver to lose concentration on the road.
Overall, smoking in the car with children under 18 or over 18 is not a good idea.