How do I get my dog to be afraid or the get the concept of cars?

Sounds like a great family dog. I would just keep him on a lead near roads and make him sit every time he is at the kerb, whether there are cars coming or not and only let him cross when you give the word. Make sure he will also come back or stop when told to come here or wait and he shoould be fine. No good making him afraid of something, that will just make him freak out whenever he is near one which wont help the situation at all. Dogs dont really have much road sense so we have to use our own.