[mjevans]

It may also simply be that they're slowing down and actually waiting to respond to problems instead of trying to get things to work as fast or easily as possible.

Traffic manages to flow quite smoothly at the speed limit when a police officer is just standing around somewhere... (but there's usually a major bottleneck right upstream of that observation point as everyone panics and straightens up their focus).

Similarly, it is amazing how disruptive something worthy of gawking at can be. A curve in the road, a car safely on the shoulder, flashing lights that scream "PAY ATTENTION TO ME": all of those things seem to result in gawker-block.

Self driving cars really can't save us quickly enough.

[dsfyu404ed]

Your police car example is pretty ignorant of the negative upstream affects of the police car. You may as well say traffic is no longer in a traffic jamb once you're past the point of the jamb.