The idea of my project is to make a free path to an emergency vehicle approaching a traffic junction. The emergency vehicle will have a RFID tag installed in it, which has to get detected a few kilometers prior to the traffic junction, for this i am using a RFID reader and when the RFID reader detects a tag, it has to send a message signal with the help of GSM module to the traffic control system to make the particular lane ON (Green). The traffic light system is done with the help of ARDUINO board. I need help to know that when the RFID detector detects a tag,how can i send a message signal from GSM module to the ARDUINO and make the lane ON by overriding the traffic light program.I want to know how to interface RFID detector and GSM module to send a message signal and upon receiving the message signal the traffic light signal has to change.