Brent ToderianDec 10, 2022
“We found that there’s this perfect one-to-one relationship. If a city increased its road capacity by 10%, then the amount of driving in that city went up by 10%.” One of the earliest, and still one of the best articles on why building bigger roads just leads to more driving. Call it #InducedDemand, or #JevonsParadox, or the #LawOfCongestion. Via WIRED, it’s worth a read and share.
https://www.wired.com/2014/06/wuwt-traffic-induced-demand/
#cities #transportation #urbanism #city #cars
What's Up With That: Building Bigger Roads Actually Makes Traffic Worse

The concept is called induced demand, which is economist-speak for when increasing the supply of something (like roads) makes people want that thing even more. Though some traffic engineers made note of this phenomenon at least as early as the 1960s, it is only in recent years that social scientists have collected enough data to show how this happens pretty much every time we build new roads.

WIRED
Show threadTom van Vuren
@BrentToderian A RAND study found much smaller elasticities of around 0.2. https://www.rand.org/randeurope/research/projects/a-review-of-induced-travel-demand.html
A review of induced travel demand

Through an extensive literature review, researchers found evidence that road capacity improvements result in induced travel demand, but most of the evidence came from large metropolitan areas outside the UK. More evidence from local studies would be helpful to ensure induced travel demand is properly accounted for in appraisal of capacity improvements to the UK's Strategic Road Network.

Dec 11, 2022 at 9:07amWeb
Show threadDavid M. Levinson ⁂Dec 11, 2022
@tomvanvuren @BrentToderian my review found between 0.5 and 1.0
Show threadDavid M. Levinson ⁂Dec 11, 2022
@tomvanvuren @BrentToderian travel budget theory gives about 1.0 in the long run.
Show threadTom van VurenDec 12, 2022
@Transportist @BrentToderian Of course the time saving doesn't have to be consumed as car travel! We should do more mixing travel time budget theory and traditional modelling, incl checking aggregate results between base year, long term do-minimum and project cases.