[Hwang Miseon's Crisis Escape Season 4] Why Does It Get More Congested Af...

[By Hwang Miseon, Columnist, Korea Lecturer News] We tend to believe that widening roads, optimizing signals, and increasing speed will improve traffic flow. In fact, we have continuously refined systems to move faster. Yet a strange pattern keeps repeating. Even after improving efficiency, congestion often worsens at some point. There are no accidents, no clear reasons, yet the flow suddenly collapses. Why does the outcome contradict the improvement in efficiency?

Many people still give the same answer: there are simply too many cars. While it is true that higher density can lead to congestion, this explanation is not sufficient. Even at the same density, traffic sometimes flows smoothly, while at other times it suddenly breaks down. Moreover, congestion persists even after efficiency improvements. The issue is not “how many,” but something else.

If we closely examine the moment just before a breakdown, a common pattern emerges. The system does not stop all at once. Instead, the flow begins to fluctuate. Speeds become slightly misaligned, gaps turn irregular, and previously invisible interactions appear. These small differences accumulate, gradually destabilizing the flow. Eventually, the entire system comes to a halt. What we perceive as a “sudden” traffic jam had, in reality, already been signaled.

The concept that explains this signal is velocity heterogeneity (Δv). Δv represents the differences in speed among individual elements, essentially the standard deviation of speed. Though simple in concept, it is a critical indicator of system stability. Every system tolerates a certain level of variation. However, as variation increases, interactions intensify and interference expands. Ultimately, the system moves toward a state where it can no longer sustain itself.

The problem is that efficiency tends to amplify this variation. As speed increases and flow becomes faster, the differences between individual elements also grow. Some move faster, others relatively slower. This is not just diversity—it becomes a destabilizing force. As Δv increases, the likelihood of conflict rises, and the system becomes more unstable. Once this difference reaches a critical threshold (Δv*), the system can no longer maintain stability. At that point, it undergoes a transition, leading to collapse.

What is important is that this process is not gradual. We often assume congestion builds up slowly, but in reality, the system holds until a certain point and then collapses abruptly. This is why improving efficiency can paradoxically worsen congestion. Efficiency accelerates flow, but at the same time, it amplifies differences and hastens collapse.

This phenomenon is not limited to roads. It appears in all systems involving people. The same applies to organizations. As individual performance is maximized and speed increases, differences among members grow. If these differences are not managed, cooperation breaks down and the system becomes unstable. Society is no exception. When diverse speeds and directions are not harmonized, balance is lost.

We are accustomed to pursuing efficiency—faster, more, optimized. However, in doing so, we overlook a critical factor: the management of differences. Systems are not sustained by uniformity, but by controlled variation. Efficiency without managing differences ultimately creates a structure that undermines itself.

Efficiency alone does not sustain a system. Only when differences are controlled can flow be maintained.

Columnist Profile

Hwang Miseon is a disaster safety instructor who has conducted on-site safety education for citizens and students. Based on repeated observations of “stoppages” and “concentrations” in training environments, she interprets disasters not as issues of individual behavior, but as problems of space and structure. She analyzes risks in everyday environments—such as hospitals, schools, public transportation, and performance venues—through movement paths, bottlenecks, guidance systems, and exit functionality. She is currently conducting research on evacuation structure analysis using microscopic pedestrian simulation.

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