MENTAL MODEL · M3343

Triple Convergence

SystemsmediumSystems Theory

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Updated 2026-08-01

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INTRODUCTION

English translation pending.

CORE DEFINITION

Triple convergence, drawn from transport research on induced demand, explains why adding road capacity does not relieve congestion. Three groups return at once: drivers who had shifted their trips out of the peak, drivers who had diverted to side streets, and transit riders who switch back to driving. Their combined flow fills the new lanes almost immediately. The general lesson is that demand is elastic with respect to capacity, so congestion is a demand problem rather than only a supply problem.

SCAFFOLDING EFFECT

psychology

Reduce cognitive load

- Capacity trap: suspect triple convergence whenever added resources fail to improve throughput. - Trace the three returns: find the deferred, diverted, and substituted demand. - Manage demand: price, prioritize, or throttle usage instead of adding more supply.

anchor

Anchor fast decisions

Adding capacity lowers the effective cost of using the system, which releases demand that congestion had suppressed and pulls substitute behavior back into the main channel. Because demand expands elastically with capacity, the system converges on the same congested state, merely at a higher volume of traffic.

MINIMUM ACTION

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Practice this model in one real situation:

When extra resources fail to help, test whether the three returns are at work. 2. Name the deferred, diverted, and substituted demand sources explicitly. 3. Estimate induced demand before funding any expansion. 4. Apply pricing, priority, or throttling to hold demand at a manageable level. 5. Re-measure after the demand controls are in place.

Check to track your progress (stored locally)

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Source support: Explicit

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iasdc.whu.edu.cnhttps://iasdc.whu.edu.cn/info/1136/1040.htmZH · Explicit
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