The observed tendency for added road capacity to generate new vehicle trips, drawn from other routes, other times of day, other modes or trips not previously made at all, so that congestion on the widened road returns toward its earlier level over time. Widely cited in transport planning literature as a reason highway widening alone rarely delivers the lasting congestion relief it promises, though the size of the effect in any given case is debated among researchers. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/
Facts
Core ConcernAdded road capacity generating new traffic that erodes the congestion relief it was meant to provide. 1 FAQs
Does widening a road actually relieve traffic congestion in the long run?
Usually not for long: induced demand means added capacity draws new trips that erode the relief.
Induced demand describes the observed tendency for added road capacity to generate new vehicle trips, drawn from other routes, other times of day, other modes, or trips not previously made at all, so that congestion on the widened road returns toward its earlier level over time. It is widely cited in transport planning literature as a reason highway widening alone rarely delivers the lasting congestion relief it promises, though researchers debate how large the effect is in any given case.
Connections
Exemplified By
The congestion article invokes induced demand as the reason lane additions fail.
Source Wikipedia: Traffic Congestion
Sources
1. Wikipedia: Induced Demand
WikipediaLead section
In transportation planning, induced demand, also called "induced traffic" or consumption of road capacity, has become important in the debate over the expansion of transportation systems, and is often used as an argument against increasing roadway traffic capacity as a cure for congestion.
- Part Of: Road Transport
In Group: Transport Planning Concepts, Lead sentence
In transportation planning, induced demand, also called "induced traffic" or consumption of road capacity, has become important in the debate over the expansion of transportation systems, and is often used as an argument against increasing roadway traffic capacity as a cure for congestion.
View the Source Wikipedia: Traffic Congestion
WikipediaExemplified By: Traffic Congestion, Lead sectionQuote, Exemplified By: Traffic Congestion, Lead section
Drivers and driver-focused road planning departments commonly propose to alleviate congestion by adding another lane to the road; however, this is ineffective as increasing road capacity induces more demand for driving.
Dissenting Readings (1 dissenting reading)
Core Concern
Steven Polzin, former director of the Center for Urban Transportation Research and former Senior Advisor at the US Department of Transportation, argues that most forms of induced demand are actually good rather than something to regret: population growth being accommodated, traffic moving out of neighborhoods onto expanded freeways, and travelers reaching their preferred trip timing are all improvements in his reading, and demand is better managed through pricing (managed lanes, tolling, congestion pricing) than through withholding road capacity. Libertarian and market-oriented analysts including Randal O'Toole, William L. Anderson and Scott Beyer have made similar arguments.
A dissenting reading, from Steven PolzinWikipedia: Induced Demand, Wikipedia
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