Why are there what look like video cameras on above traffic lights at main intersections?

At most major intersections in Houston Texas, there appears to be video cameras above each traffic light or on each of the four corner support poles. I know the city is contemplating "red light cameras" but the initiative has not been approved. What are these cameras used for? Who monitors them? Can you get a video tape of the intersection to be used for accident investigation?Why are there what look like video cameras on above traffic lights at main intersections?
These are not cameras but light sensors. Have you noticed that fire trucks and ambulances have strobe lights flashing on the front of them?

The strobe light is registered by the light sensor which flashes at a set frequency to change the traffic light to green in the direction the emergency vehicle is going.
I believe they are just for traffic monitoring since they usually point towards the oncoming lane and like here in indiana we don't have front license plates so it would be pointless to be a red light camera. Red light cameras are easy to notice, it's either a big box on the sidewalk that emits a massivly bright flash when someone blows the light or its several lights extending the length of the pole that the traffic light hangs on and emits several high intensity flashes.Why are there what look like video cameras on above traffic lights at main intersections?
They could be cameras for enforcement of red lights, but they could also be the sensors for the "smart" traffic lites. Rather than rely on timers for the red/yellow/green intervals, the sensors determine when traffic is there, and so adjusts the light changing to more efficiently deal with the traffic load.
The cameras can also be used for other law enforcement reasons such as evidence and trying to peice together a crime. As well as survailance. Not always watched, you can reference cameras from various locations at a given time if something happenend then. Going back after the fact and seeing who the terrorist talked to or something. Cameras on all the poles give you a veiw of the whole street.Why are there what look like video cameras on above traffic lights at main intersections?
Could be the same as in UK they are sensors which detect the approach of a vehicle and change the lights accordingly,or could be trafficmaster cameras that detect congestion and then relay it to your in car traffic system.
the can be used like you said to get people running red lights, also can be used for monitoring the flow of traffic so they can change the lights so traffic dose not get backed up. Yes the tape can be used for investigation the officers will use anything they have to help them figure out what happened