What if all the cars went at the same time?

Have you ever waited in a car at a red light? Listen, and you can hear the engine hum softly. Across the road, other cars roll past while you wait.

Then the light turns green, and your car gets to go. So you might wonder, what if all the cars went at the same time?

Think about the spot where two roads cross. This spot is called an intersection, which means a place where roads meet. Drivers from both roads cross it to get where they are going.

At the intersection, the drivers take turns. Drivers on one road go while drivers on the other road wait. That way, the middle stays open for the moving cars.

Now let's imagine every driver going at once. Cars from one road roll into the intersection. Cars from the other road roll in too, at the very same moment.

But each car needs its own space on the road. Two cars cannot fit in one spot at the same time. So the cars would bump into each other in the middle.

The drivers would stop, with their cars nose to nose. Now the stopped cars block the whole intersection. What do you think happens to the cars still coming down the road?

Those drivers have to stop too, one car behind another. The line of stuck cars grows longer and longer. Soon nobody can go forward, and nobody can turn back.

If all the drivers went at once, their cars would bump in the intersection. Two cars cannot fit in one spot, so every car would get stuck.

So at the intersection, the drivers keep taking turns. One road rolls while the other road waits, engines humming softly. And every car gets where it is going.