According to the history books, the first traffic light was displayed in 1868 in London to regulate pedestrian and buggy traffic outside Parliament. Red meant stop. Green meant go. History does not record when the first horse ran a red light, but I suspect it was soon after. Since then, almost all of us regard the habit of running red lights as a dangerous one. Most of us stop at red lights. We assume that other people will as well. Unfortunately, a few people don't. So, people get hurt, sometimes badly.
If everyone obeyed the law, we would not need the police. But, they don't, so we do. There are hundreds of intersections in the City of St. Louis. And scores of busy ones. At the busiest intersections, thousands of cars and pedestrians pass each other every day. Keeping them all, motorists and pedestrians, safe is an important part of the police department's job. But it is not the department's only job, and they simply cannot patrol every dangerous intersection. Hence, red light camera enforcement. Red light cameras make intersections safer. Safer for drivers. Safer for pedestrians. It is obvious in the numbers. After the first few months of a red light camera, the number of violations go down, a lot. Fewer people are running red lights. This means that most drivers change their behavior when they believe there is a risk that they will be caught and fined. That is, for me, the reason to have them, and the reason not to make their operation illegal in Missouri.
If you don't want to pay a red light ticket, don't run a red light.