camera traffic disruption

To night the traffic from top ryde to homebush bay was bumper to 
bumper at aprox 7 pm.
  Half way along homebush drive I found out why .The police had a camera 
on the side of the road
  and two cars with fla****ng lights 100 metres further on pulling up cars.
  The camera could not be speed camera as the police had people almost 
at standstill.
  I assume that they were using the newfangled camera databank checking 
plates for villains
  and unregistered vehicles etc.
  You would assume that they would check what chaos that they were 
causing for miles behind them
  but they were probably too busy to worry about the ordinary citizen.