The scenerio: Main road direction is north and south. It has no stop sign and speed limit is 30 mph. Side road comes into main road at 90 degrees (going east and west) and has a stop sign where it meets the main road. Car A is traveling south on main road at just about 30 mph. Car B is on side road approaching main road traveling east. They stop at the stop sign and then pull out to cross the main road. The driver of car B says they did not see car A approaching from the north. Car A attempts to avoid the collision by swerving to the right to get behind car B and brake hard but they hit the back of car B with the left side of car A. Who is at fault in this accident?