You could breakdown anywhere but in a heavy traffic hot weather situation there is a s good as chance as anywhere. An American new information piece on the risks of breakdown down within a heavy traffic situation explains what the insurance companies tell you what to do in these situations. There is some conflict to information we are often given, that you should get out of the car and stay well away from the vehicle here in the UK. We can only assume that the difference is if there is somewhere safe to stand and that you do not have to cross traffic to get there especially if the traffic is at high speed. Having a breakdown cover company to ring at this point could make this situation a little more bearable.