[Fjolsvith]

I used to be a computer technician. Sometimes I arrived at a customer's office and the perplexed person couldn't explain why his computer suddenly started working. I developed a theory I called the "Tech Threat Syndrome", which posed that computers occasionally hid their problem whenever a technician appeared, so as to embarrass their user.

[lolc]

My theory around this is rather mundane: People behave more in the way they were taught when an authority is around. That makes a lot of computer problems go away when a techie shows up because people avoid taking shortcuts when they're being watched.

In my view this is sufficient to explain the phenomenon.

[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.

[marcosdumay]

It's a widely believed theory, formulated (and verified) independently many times through history.