can you give more details and circuit diagram...

Emergency vehicle alert system transmits signals from one or more emergency vehicles to nearby vehicles. When a switch in the emergency vehicle is pressed, a transmitter broadcasts a unique identifier for the vehicle.position, speed, route, and direction of travel of the emergency vehicle can also be transmitted to provide alert information to vehicles in the path of the emergency vehicles. The information presented can include audio and visual displays such as lights, voice warnings, moving map display with symbols representing the vehicles' position relative to one another, and a display providing identification and distance information.

This system is a computerised one and uses many centralised servers and network interfaces and transmitters fitted on the emergency vehicles and recievers fitted on the traffic light posts. The job of computer is to recieve and decode the signal, Determine the route of the emergency vehicle, identify other vehuicles in the route , transmit CLEAR signal to th e commuter vehicles, Control traffic light stops , Pack and transmit the signals.

More details and detailed report download:
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Also see,
http://patentstorm.us/patents/7236101/description.html