Parking guidance and information (PGI) systems, or car park guidance systems, present drivers with dynamic information on parking within controlled areas. The systems combine traffic monitoring, communication, processing and variable message sign technologies to provide the service. Modern parking lots utilize a variety of technologies to help motorists find unoccupied parking spaces, car location when returning to the vehicle and improve their experience. This includes adaptive lighting sensors and parking space led indicators (red for occupied, green for available and blue is reserved for the disabled; above every parking space), and indoor positioning system (IPS). PGI systems are a product of the worldwide initiative for the development of intelligent transportation system in urban areas. PGI systems can assist in the development of safe, efficient and environmentally friendly transportation network.[1] PGI systems are designed to aid in the search for vacant parking spaces by directing drivers to car parks where occupancy levels are low. The objective is to reduce search time, which in turn reduces congestion on the surrounding roads for other traffic with related benefits to air pollution with the ultimate aim of enhancement of the urban area. A Parking Guidance System (PGS) have different elements:[2] Detectors LED indicators Zone Controllers Data / Intermediate Controllers Central Control System Signs Detectors can use different technologies, such as: Ultrasonic detectors Forward mounting sensors. Camera based detectors.[3] Infrared based detectors. Magnetic sensors that detect vehicles via changes in earth's magnetic field. Some use combinations of above technologies to detect vehicles. Quoted from Wikipedia