Powerline Down
On my way to work one morning before dawn and rush hour, I saw fire trucks with bright flashing lights at an intersection where I normally turn right. I assumed there had been a crash, so I moved over to the sidewalk to skirt the blockage.
I had to stop suddenly because I then saw a cable laying on the sidewalk. It ended up the intersection was blocked due to the powerline being down, and the emergency personnel were focused on motor vehicles and did not see me approaching.
What I learned from that was a) those bright lights make it really difficult to see what is going on and b) I shouldn't assume I know what is going on.
My practice now when there are emergency lights is to dismount and walk around the area with caution.