If the number of cars on the main road is so great that you need to interrupt the flow in order to let yet more cars on it, you're contributing to yet more traffic congestion.Actually, about 16 years ago, traffic lights were introduced on entrance ramps to the Long Island Expressway. The idea was to prevent cars from entering the highway during rush hour. That demonstrates an appropriate use of traffic lights -- to improve the flow of traffic rather than to impede it.
It's inefficient to force several cars to stop for the sake of one or two cars that are already stopped. Forcing a car to stop and then accelerate back up to cruising speed is a significant waste of gas. In fact every time a driver applies the brake, he or she "throws away" the fuel that was used to accelerate the car. And acceleration is what uses the most fuel.
Many of these intersections are so small that when cars turn onto them from the main road, the cars trigger the Hall effect sensor that causes the light to cycle. Thus, the light turns red for those who navigate the main road even when there's no car to yield to! More waste!You can solve both problems simply by installing (or moving) the sensors farther back from the intersection and decreasing the sensitivity. That way the light won't cycle unless there are a few cars queued up. It might be a good idea to change the mode to blinking red-yellow during non-peak hours to allow cars to enter the main roadway whenever it's clear, but then have the light switch to give the right-of-way to the smaller roadway when enough cars are waiting.
I can imagine the day when every intersection will have a traffic light. Hopefully I'll be dead by then. Or perhaps traffic lights will be part of a Intelligent Vehicle System that's designed to route traffic for maximum efficiency. Lights will be used to tell motorists when it's safe to enter the intersection rather than stop other cars to allow them to enter.