I'm Waiting on That!

I was driving into work.  When I came to I-4, the traffic was not moving.  I saw police lights up ahead. I thought it was a major accident.  We slowly edged toward the accident.  By the time I got up to it, I could not understand what the wait was.  Two cars had bumped each other.  There was a police car.  No lanes were blocked.  I can understand the left lane going slow, because they are near the accident.  Why the rest?