Starting at figure 2A, the cars depart from the jam in sequence. It moves leftwards as it eats into the traffic jam. There is a second important thing to notice. While some cars are still jammed, more cars are piling up behind them at the trailing end of the jam. The traffic jam is like a solid object whose front end is evaporating and whose back end is growing like a crystal.
Cars move left to right, yet watch the group of stopped cars.
The stoppage is creeping slowly upstream, in the opposite direction to the moving cars. The accident is gone, but a moving wave of stopped cars remains behind. It's a traffic-clot in the blood vessel. It's a travelling wave of traffic-condensation. These sorts of travelling waves are common during heavy traffic conditions.