1. When black car is merging left and red car starts to merge right, the black car is in his blind spot. Despite the blind spot, Red should be aware of Black's presence, just as Black should have been aware of Red.
2. Black merges with zero following distance behind Red.
3. Initially, I thought Red brake-checked Black (a stupid thing to do when Black's so close behind), but on review, I think Red's only responding to what's directly in front, though Red may have moved left to block the seemingly aggressive action from Black...
4. As the Red/Black interaction is going on, you can catch a glimpse of the silver car ahead putting his brakes on. So perhaps the brake check was actually just maintaining a safe following distance from the car ahead?
5. Black didn't get on the brake, even after being brake-checked from zero distance. Was Black even off the gas? And still didn't get on the brake until he's spun to nearly a complete stop.