Almost all of you are wrong. Of course it can be the car in fronts fault if they pull out in front of someone and then slam on their brakes. It all depends on how long the time was between pulling out, and when he put his brakes on.
Dex, you are just plain wrong, in Qld anyway. It is the merging drivers sole responsibility to join the flow of traffic safely. They have to give way, just as you give way at a T-junction. The rules are the same - except that you must adjust your speed to that of the traffic that you are merging with. Nobody has to take any action to let someone in. The Qld rules are very clear on this point.
The best thing your son can do is to report it to the police. Tell them exactly what happened, and see what they say. His ins. co. won't be interested - legally, they can't be, as there is no contract between them and your son for damage to his car. If there is no damage to the other party then they won't be interested at all. How much is the damage to his car? The other thing he could do is to repair the damage and then sue the other guy for the costs. But that could get expensive ....
