my friend..

here is the answer which is true ..[i work in this field]

the sensors are far enough from the stopline..
designers make sure that these sensor must be before the line there.. to prevent miss the sensor by drivers..

and who says that in doha it is 99% pretimed??
NOT TRUE..

now the state begins to use the smart signals that is better than sensor ..cuz of having many sensors along the lanes.... to on/off at the best time to..

regards..