The Simple Solution to Traffic

Stuck at an intersection, you always watch unfold the Fundamental Problem of Traffic. On green, the first car accelerates, and then the next, and then the next, and then the next, and then you, only to catch the red. Had the cars accelerated simultaneously, you would have made it through. Coordination—not cars—is the problem, because we are monkey drivers with slow reaction times and short attention spans. Even if we tried getting everyone to press the pedal on "3-2-1-now," it would be challenging. This dis-coordination limits how many cars can get through an intersection, and when one backs up to the next, that's when city-sized gridlock cascades happen, taking forever to clear.

In general, more intersections equal more dis-coordination, which equals more traffic. This is the motive behind big highways: no intersections. Splits and merges, yes. Intersections, no. No stopping, no coordination problems, no traffic. Well, that's the theory anyway. Intersections outside of a highway will back up onto it. Again, because human reaction times limit how many cars can escape the off-ramp when the light changes. But, even without intersections, there would still be traffic on the highway. Traffic can just appear.

Take a one-lane highway with happy cars flowing until a chicken crosses the road. The driver who sees it brakes a little, the driver behind him doesn't notice immediately and brakes a little harder than necessary. The driver behind him does the same until someone comes to a complete stop, and, oh look, cars approaching at highway speeds must now stop as well. Though the chicken is long gone, it left a phantom intersection on the highway. This is what's happened when you're stuck in traffic for hours thinking, "There must be a deadly pile-up ahead," and then suddenly, the traffic's over with no wreckage in sight, to your relief if you're a good person and mild annoyance if you aren't.

You just pass through a phantom intersection, the cause of which is long gone. And this phantom intersection moves. It's really a traffic snake slithering down the road, eating oncoming cars at one end and pooping them out the other. On a ring road, a single car slowing down will start an Ouroboros of traffic that will last forever, even though there's no problem with the road. If the drivers could coordinate to accelerate and separate simultaneously, easy driving would return. But they can't, so traffic eternal.

On highways, traffic snakes grow if cars are eaten faster than excreted, and they shrink if excreted faster than eaten, dying when the last car accelerates away before the next car must stop. Now, in multi-lane highways, there needs be no chicken to start gridlock. A driver crossing lanes quickly with cars too close behind is enough to birth a traffic snake that lives for hours and leagues. It's this quick crossing that causes drivers behind to over-brake and begin a chain reaction.

But we can make traffic snakes less likely by changing the way we drive. Your goal as a driver is to stay the same distance from the car ahead as from the car behind at all times. Tailgating is trouble. Not just because it makes accidents more likely but because you as the tailgater can start a traffic snake if the driver ahead brakes. Always in the middle! This gives you the most time to prevent over-braking but also gives the driver behind you the most time as well. And when stuck in traffic, this rule would get all cars to pull apart the snake faster.

That's the simple solution to traffic: getting humans to change their behavior, perhaps by sharing this video to show how and why traffic happens, why tailgaters are trouble, and how we can work together to make the roads better for all. The End. Except, yeah... wishing upon a star that people are better than they are is a terrible solution. Every time. Instead, what works is a structurally systematized solution which is exactly what self-driving cars are.

Self-driving cars can just be programmed to stay in the middle and accelerate simultaneously. They'll just do it. The more self-driving cars at an intersection, the more efficient the intersection gets. A solid lane of self-driving cars vastly increases throughput. Hmm, actually! If you ban humans from the road (which we should totally do anyway), you can get rid of the intersection entirely. After all, a traffic light is just a tool for drivers on one road to communicate with drivers on another, poorly and coarsely. Red equals "Don't go now, we are coming through the intersection." Green equals "good to go."

But self-driving cars can talk to each other at the speed of light. With that kind of coordination, no traffic light necessary. Just as with the highway, the best intersection is no intersection. Humans will never drive this precisely. At the intersection, the fundamental problem with traffic that you watch unfold, as well as everything, is people. So the real simple solution to traffic is no more monkeys driving cars.

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