On my way home from work, approaching a group of cars when I noticed the taxi swerve out of his lane, clip the back of a van, veer the other way, and strike a gold car. The van never stopped, having maintained control. The taxi lost control into the ditch on the right and the gold car spun out across my path into the center wall. I pulled over and made sure everyone was okay, even had a few words with the gold car driver and passenger. Driver stated he was trying to get into the middle lane and had almost finished doing so when a taxi slammed him. Video shows he didn't see the taxi in the middle. After I talked with him I hand signaled across the highway to make sure taxi occupant and driver were okay, I didnt cross the highway. I informed gold car driver that I would take his number and send him the video link because I couldn't make sense of the situation when it happened so fast. Went home before cops arrived and uploaded video for driver to see. He probably won't be happy.