The camera to install at junction, get live stream and I can add virtual loop sensor on the road to detect and count vehicles.
It can also detect traffic congestion level.
Vehicle detection loops, called inductive-loop traffic detectors, can detect vehicles passing or arriving at a certain point, for instance approaching a traffic light or in motorway traffic. An insulated, electrically conducting loop is installed in the pavement. 
Vision based loop sensor requires no pavement cut. I can add/remove/modify loop sensor whenever i need it.
I will use raspberry pi 2 and raspberry pi camera v1.3
i will record video from traffic junction/grab it from online and process at home instead of installing raspi on the junction.
for video proof, i will make a simple vehicle count and detection with mini size vehicle (e.g. remote car) to demonstrate the project output.