The Fundamental Law of Road Congestion¶
Duranton, G., & Turner, M. A. (2011). The Fundamental Law of Road Congestion: Evidence from US Cities. American Economic Review, 101(6), 2616-2652.
Cited by¶
4 citations across 4 artifacts.
Each citation links to the sentence it supports in the citing article.
Primes¶
- Jevons Paradox
- The efficiency improvement is widening a highway from two lanes to three on a congested corridor — a genuine per-trip gain in throughput.
This sourceEmpirically shows that vehicle-kilometers travelled rise roughly one-for-one with lane-kilometers, so road expansion induces proportional demand.
Supported in partVerified against the work's full text
The paper's model says adding lane-kilometers lowers the cost of driving at any traffic level, which is the per-trip gain; the two-to-three-lane corridor example is not in it.
“Increasing the supply of road lane kilometers from R to R′ reduces the average cost of driving for any level of vkt.”
- The efficiency improvement is widening a highway from two lanes to three on a congested corridor — a genuine per-trip gain in throughput.
- Parkinson's Law
- In highway capacity, added lanes draw commensurate new traffic as travel-time slack invites additional trips.
This sourceEmpirically establishes that vehicle-kilometers traveled increase roughly one-for-one with lane-kilometers of roadway — induced demand quantified.
SupportedVerified against the work's full text
Duranton and Turner find VKT rises in proportion to lane kilometers, with demand for travel very elastic to the time cost of travel that roads lower.
“That is, an increase in lane kilometers induces an exactly proportional increase in vkt.”
- In highway capacity, added lanes draw commensurate new traffic as travel-time slack invites additional trips.
Mechanisms¶
- Capacity Expansion Trigger
- Expanding a channel whose demand is ungoverned can induce more demand — the newly freed capacity is consumed as fast as it is added, and the channel saturates again at a higher cost base.
This sourceFinds that added road capacity induces roughly proportional additional travel and is unlikely to produce lasting congestion relief.
- Expanding a channel whose demand is ungoverned can induce more demand — the newly freed capacity is consumed as fast as it is added, and the channel saturates again at a higher cost base.
- Traffic Lane
- And a common misuse is treating a new lane as pure capacity: adding or widening a lane often just draws more of that class
This sourceFinds traffic growth after capacity expansion and persistence of congestion rather than relief.
- And a common misuse is treating a new lane as pure capacity: adding or widening a lane often just draws more of that class
Verification¶
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