There's only one or two in my area that would warrant adding signals, but they're only backed up during rush hour by people trying to take a "shortcut" around the highway traffic. So I consider them kinda self limiting due to the traffic. Not many more people try to take that route at that time when they're aware that it's clogged in the direction of rush hour traffic.

The other is right next to a private school and is only clogged because nobody uses their bus service, so, I don't have any sympathy for the parents.