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Why the next lane moves 'faster' than yours in a traffic jam: the scientific explanation

You're stuck in a traffic jam, you look to your left and notice that the cars ahead are moving much more quickly. You decide to change lanes. As soon as you do, the lane you left seems to flow more freely, while yours gives the impression of being slower. Thousands and thousands of drivers experience this scene daily, especially in cities. Everyone arrives at their destination with the feeling of having spent a lot of time in the wrong lane. But the reality is quite different from what we imagine; it's quite distinct.

The key lies in how our brain perceives movement and progress. It seems a little strange, but don't worry, it's easy to understand: Canadian doctor Donald Redelmeier, along with statistician Robert Tibshirani, studied this phenomenon and discovered that, in most cases, this feeling of being in the slower lane is just an illusion. They analyzed real traffic and concluded that, objectively speaking, lanes tend to move at similar speeds. Even so, your perception as a driver tells a different story. Why?

The so-called "selection bias" also plays an important role. This means that we only notice the lanes that are moving faster at a given moment. But if there is another lane next to us that is moving more slowly, we don't even notice it, because it ceases to be a visual reference point. It's a kind of automatic filter that prevents us from realizing that we are not always the slowest.

It turns out that impatience also plays an important role. When changing lanes, you have a certain sense of control because you feel you are doing something to move forward (even if, in practice, the benefit is minimal or even nonexistent). This need for action drives you to make quick decisions from which you expect to obtain benefits. And if, in the end, this benefit does not materialize, or you do not perceive it as such, the persistent feeling is that, once again, you made the wrong choice.

In the few stretches of our highways with three lanes in each direction, the phenomenon intensifies, because the more lanes, the more comparisons the brain makes. And each of these comparisons reinforces the idea that there is always a better option than the one we choose.

Which lane is the fastest? The one you're not in…Math explains when the lane next to you is actually faster: it's a matter of probability. On a two-lane highway, you have a 50% chance of being in the faster lane—which means you also have a 50% chance of being in the slower lane.

On three-lane highways, the probability of being in the faster lane is one in three, or 33%. With four lanes, the chances of hitting the fast lane drop to 25%. And on five-lane highways, it drops to 20%.

But there's a variable in this calculation: when drivers in the slower lanes start changing lanes, they have to cut in front of another car, which will reduce its speed and start a ripple effect that will eventually stop the line. So, in addition to the fixed probability of being in the wrong lane, this probability varies with each car that decides to change lanes, which reduces the chances of you being in the fast lane to almost zero.

The other situation is when all lanes are truly slow, something that happens in narrowed lanes where drivers "zip" (take turns to pass through the bottleneck). Most of the time the speed of the lines is the same, but the line next to you seems to move faster simply because we are selfish. And that's not wrong or bad. It's just a natural perception explained by what psychology calls illusory correlation.

Illusory correlation is the assumption that there is a clear correlation between two items when, in fact, there isn't. It's something we do when we need/want to make decisions but have limited information.

That's why we think there's a correlation that doesn't exist, for example, thinking that the rain always decides to fall at the time we leave work/school/university. Obviously, it doesn't fall at 6 PM because you need to leave a covered and protected place, but because coincidentally the vapor condensed at 6 PM and returned to the ground as rain.

Similarly, when we are stuck in traffic and see the line next to us moving, our intuition relates the fact that our line is stopped to the most evident element in our environment: ourselves, our desire to arrive quickly, our wish to be moving.

This makes us notice more how many cars pass us in the moving line than how many cars we pass when our line is actually moving. And this also has a logical explanation: when we are stopped, we are the point of view. We see five, ten, fifteen cars passing by and, thinking about ourselves (our desire to arrive, our wish to be moving), we realize that we are standing still and falling behind.

The feeling that the lane next to you is moving faster in a traffic jam is often an optical and memory illusion, known as confirmation bias. The neighboring lane seems faster because you notice when it moves forward, but ignore when it stops, focusing only on your frustration at being stuck.

Point of View Illusion: When stopped, we perceive cars passing us more intensely.

Confirmation Bias: You only remember the times when you changed lanes and the old lane became faster, and not the times when changing was indifferent.

Momentary Effect: The next lane may move faster momentarily when a car changes lanes, but in the long term the average speed between lanes is usually the same.

"Zipper" Effect: Constantly changing lanes may, in some scenarios, be a little faster, but it is a risky maneuver and increases the risk of accidents.

In summary: in most cases, all lanes are moving (or stopping) at the same average speed, and changing lanes only increases stress and the risk of collisions.