Induced demand

In other words, as a good or service becomes more readily available and mass produced, its price goes down and consumers are more likely to buy it, meaning that the quantity demanded subsequently increases.

[6] According to CityLab: Induced demand is a catch-all term used for a variety of interconnected effects that cause new roads to quickly fill to capacity.

The effect was recognised as early as 1930, when an executive of a St. Louis, Missouri, electric railway company told the Transportation Survey Commission that widening streets simply produces more traffic, and heavier congestion.

[16][17] J. J. Leeming, a British road-traffic engineer and county surveyor between 1924 and 1964, described the phenomenon in his 1969 book, Road Accidents: Prevent or Punish?

By 1998, Donald Chen quoted the British Transport Minister as saying "The fact of the matter is that we cannot tackle our traffic problem by building more roads.

"[21] According to city planner Jeff Speck, the "seminal" text on induced demand is the 1993 book The Elephant in the Bedroom: Automobile Dependence and Denial, written by Stanley I. Hart and Alvin L.

These cost determinants change often, and all have variable effects on demand for transport, which tends to be dependent on the reason(s) as well as method of travel.

The elasticity of demand for transport differs significantly depending on the reason people are choosing to travel initially.

[22] This exemplifies the fact that activities that yield a high economic benefit, in this case, financial gain in the form of income, tend to be inelastic.

In the long term, this effect alters land use patterns as people choose homes and workplace locations farther away than they would have without the expanded road capacity.

These development patterns encourage automobile dependency which contributes to the high long-term demand elasticities of road expansion.

In real world applications, policymakers must consider the benefits of new infrastructure with the potential negative impacts on the environment, public health, and social equity.

An example of this is the Expansion of Heathrow Airport, where hopes of additional runways would spur economic growth within the UK: increasing both the amount and frequency of direct flights.

[32] In 2020, the court of appeal ruled the expansion plans illegal due to the ministers’ lack of consideration towards the government’s commitments to climate change.

[33] In contrast to negative externalities, Bogotá, Colombia, has been recognized as a success story in managing induced demand for transportation by investing in new bike infrastructure.

[37] Similar arguments have also been made by libertarian transportation policy analyst Randal O'Toole,[38] economist William L. Anderson,[39] transportation journalist and Market Urbanist director Scott Beyer,[40] Professor of City and Regional planning Robert Cervero,[41] studies such as from WSP and Rand Europe,[42] and numerous others.

This is supported by several regression analyses that suggest a high correlation between destinations taking a proactive approach in order to encourage producers/studios to film at their location, and the tourism success in the area after the release of the movie.

This is exemplified by a Travelsat Competitive Index study that indicated that in 2017 alone, approximately 80 million tourists made the decision to travel to a destination based primarily on its featuring in a television series or film.

This follow-up study was carried out by Sally Cairns, Carmen Hass-Klau and Phil Goodwin, with an Annex by Ryuichi Kitamura, Toshiyuki Yamamoto and Satoshi Fujii, and published as a book in 1998.

[45] A third study was carried out by Sally Cairns, Steve Atkins and Phil Goodwin, and published in the journal Municipal Engineer in 2002.

Taking the results as a whole, there was an average reduction of 41% of the traffic flows on the roads whose capacity had been reduced, of which rather less than half could be detected as reappearing on alternative routes.

There was a large variation around these average results, with the biggest effects seen in large-scale pedestrianisation in German town centres, and the smallest seen in small-scale temporary closures with good alternative routes, and small reductions in capacity in uncongested streets.

Cairns et al. concluded that: ... the findings reinforce the overall conclusion of the original study—namely, that well-designed and well-implemented schemes to reallocate roadspace away from general traffic can help to improve conditions for pedestrians, cyclists or public transport users, without significantly increasing congestion or other related problems.

[46]The European Union have produced a manual titled "Reclaiming city streets for people"[47] that presents case studies and methodologies for traffic evaporation in urban areas.

An early example of the reduced demand effect was described by Jane Jacobs in her classic 1961 book The Death and Life of Great American Cities.

[11] Two widely known examples of reduced demand occurred in San Francisco, California, and in Manhattan, New York City, where, respectively, the Embarcadero Freeway and the lower portion of the elevated West Side Highway were torn down after sections of them collapsed.

[48] A New York State Department of Transportation study showed that 93% of the traffic which had used the West Side Highway was not displaced, but simply vanished.

[citation needed] Of the approximately 200 pedestrian malls created in the US from the 1970s on, only about 30 remained as of 2012, and many of these became poorer areas of their cities, as lack of accessibility caused commercial property values to decline.