Downs–Thomson paradox
The Downs–Thomson paradox (named after
Although consistent with
Consequence
The general conclusion, if the paradox applies, is that expanding a road system as a remedy to congestion is ineffective and often even counterproductive. That is known as
A 1968 article by Dietrich Braess[2] pointed out the existence of the counterintuitive occurrence on networks: Braess's paradox states that adding extra capacity to a network, when the moving entities selfishly choose their route, can in some cases, reduce overall performance.
There is interest in the study of this phenomenon since the same may happen in
Restrictions on validity
This section's factual accuracy is disputed. (September 2022) |
According to Downs, the link between average speeds on public transport and private transport applies only "to regions in which the vast majority of peak-hour commuting is done on rapid transit systems with separate rights of way. Central London is an example, since in 2001 around 85 percent of all morning peak-period commuters into that area used public transport (including 77 percent on separate rights of way) and only 11 percent used private cars. When peak-hour travel equilibrium has been reached between the subway system and the major commuting roads, then the travel time required for any given trip is roughly equal on both modes."[3]
See also
- Braess's paradox
- Induced demand
- Marchetti's constant, a corollary of which is that decreasing congestion may increase the distance people are willing to commute and so increase the traffic burden
- Lewis–Mogridge position
- Jevons paradox, an increase in efficiency tends to increase (rather than decrease) the rate of consumption of that resource
- Unused highway – Roads that were closed or never used
References
Notes
- ISBN 978-1-349-11798-7.
- S2CID 39202189. Retrieved 22 June 2020.
- ISBN 9780815796558.
Bibliography
- Braess, Dietrich; (1968), Über ein Paradoxon aus der Verkehrsplanung, translated from German as On a Paradox of Traffic Planning by Dietrich Braess, Anna Nagurney, and Tina Wakolbinger (2005), Transportation Science 39/4, 446–450
- Downs, Anthony; (1992), Stuck in Traffic: Coping with Peak-Hour Traffic Congestion, The Brookings Institution, Washington (DC), ISBN 0-8157-1923-X
- Mogridge, Martin J. H.; (1990), Travel in towns: jam yesterday, jam today and jam tomorrow? Macmillan Press, London, ISBN 0-333-53204-X
- Thomson, John Michael; (1972), Methods of traffic limitation in urban areas. Working Paper 3, OECD, Paris