what happen on route 16?

This morning while driving to work I got to route 16 (where it's either Somerville, Arlington, or Medford I'm not sure which) and the road was totally packed (perhaps closed) up almost to the Powderhouse rotary where it meets 16. No one was moving it seems like for a loooong time.

I sat and waited for a while then decided to turn around and go back up 16 and take Broadway in Arlington to 3A instead. Before turning around - I watched an SUV turn around but then never bothered looked behind themselves to back up and slammed into another car that had also turned around and was beeping to the SUV to stop. Ooooops. Who backs up and assumes no one is behind them so no need to look???

When I turned around I could see that there were some cop lights up ahead so something was going on. Anyone know?

Then I ended up behind a woman driving with a banana clip in her hair. REALLY? A banana clip? FYI: those haven't been in style since '85 and really should have NEVER been in style in the first place. Having a big plastic thing in your hair that covers the front of your hair to the back is not very attractive.