vehicle speed controller NEED HELP!!

[tinubegood]

hi everybody!
 
    I'am building my final year project(automatic vehicle over speed controller), my
project is divided in 2 units ,1 in car & the other is transmitter placed on the road.
            the transmitter on the road has to transmit the max speed limit on that particular road. the receiver in the car receive this speed limit information & then monitor the speed of the vechile, if speed exceeds the limit then reduce it.
        but what kind of transmitter on the roadside should i use(it should transmitt information quickly). plz help me in finding the best suited transmitter. ??? ??? ???

waiting for reply,  thanks

 

[audioguru2]

A little radio transmitter won't transmit far enough. You will need to get a licence to operate your own radio station. Then you can use a tranmitter that is powerful enough to cover the entire length of the road. A high antenna will help.

Instead of transmitting the speed limit over the entire length of the road, have a low power transmitter at each end. When a car is near the 1st one then the speed controller is set and is turned on. When the car gets near the 2nd one then the speed controller is reset and is turned off.