Nooooo Not a filter! While it will fix the problem of people sitting in the middle you then get some drivers sitting in the middle of the road with the lights on green waiting for the filter to come on, and unfortunately it will not stop a driver turning in front of someone when both are on green.
I looked today and all lights are only on red for about 1 second, maybe if this was 3 seconds then the middle of the junction could clear easier (providing people don’t cause an obstruction by sitting in the middle of the road waiting to turn because they can see a red light, after they passed the stop line 10 seconds earlier)?