Some drivers are pulling up at traffic lights and stopping so far back that they are not triggering the sensor buried in the road. This then does not allow the electronics controlling the signals to see that there is a vehicle waiting to get a green light. The sensors have been placed to cover a whole car length as measured from the white stop line painted between left and right curbs. You are supposed to pull up just behind the white line, not a whole car length back!!!
You wouldn’t pull up to a stop sign a whole car length back from the white line so don’t do it at a traffic signal!