Editing Induced demand (section)

===History===
Latent demand has been recognised by road traffic professionals for many decades, and was initially referred to as "'''traffic generation'''". In the simplest terms, latent demand is demand that exists, but, for any number of reasons, most having to do with human psychology, is suppressed by the inability of the system to handle it.  Once additional capacity is added to the network, the demand that had been latent materialises as actual usage.<ref name=vanderbilt>Vanderbilt, Tom (2008) ''Traffic: Why We Drive the Way We Do (and What It Says About Us)'' New York; Knopf. pp.154-156. {{ISBN|978-0-307-26478-7}}</ref>

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.<ref>''Report of the Transportation Survey Commission of the City of St. Louis'' (1930), p.109, cited in Fogelson, Robert M. (2001) ''Downtown: Its Rise and Fall, 1880–1950'' New Haven, Connecticut: Yale University Press. p.66. {{ISBN|0-300-09062-5}}</ref>  In New York, it was clearly seen in the highway-building program of [[Robert Moses]], the "master builder" of the [[New York City]] area. As described by Moses's biographer, [[Robert Caro]], in ''[[The Power Broker]]'': <blockquote>During the last two or three years before [the entrance of the United States into World War II], a few planners had&nbsp;... begun to understand that, without a balanced system [of transportation], roads would not only not alleviate transportation congestion but would aggravate it.  Watching Moses open the [[Triborough Bridge]] to ease congestion on the [[Queensboro Bridge|Queensborough Bridge]], open the [[Bronx-Whitestone Bridge]] to ease congestion on the Triborough Bridge and then watching traffic counts on all three bridges mount until all three were as congested as one had been before, planners could hardly avoid the conclusion that "traffic generation" was no longer a theory but a proven fact: the more highways were built to alleviate congestion, the more automobiles would pour into them and congest them and thus force the building of more highways &ndash; which would generate more traffic and become congested in their turn in an ever-widening spiral that contained far-reaching implications for the future of New York and of all urban areas.<ref>{{harvnb|Caro|1974|p=897}}</ref></blockquote>  The same effect had been seen earlier with the new [[parkways]] that Moses had built on [[Long Island, New York|Long Island]] in the 1930s and 40s, where <blockquote>... every time a new parkway was built, it quickly became jammed with traffic, but the load on the old parkways was not significantly relieved.<ref>{{harvnb|Caro|1974|p=515}}</ref></blockquote>  Similarly, the building of the [[Brooklyn–Battery Tunnel]] failed to ease congestion on the [[Queens-Midtown Tunnel]] and the three [[East River]] bridges, as Moses had expected it to.<ref>{{harvnb|Caro|1974|p=911}}</ref> By 1942, Moses could no longer ignore the reality that his roads were not alleviating congestion in the way he expected them to, but his answer to the problem was not to invest in mass transit, it was to build even more roads, in a vast program which would expand or create {{convert|200|mile|km|-2|abbr=off|sp=us}} of roads, including additional bridges, such as the [[Throgs Neck Bridge]] and the [[Verrazano Narrows Bridge]].<ref>{{harvnb|Caro|1974|pp=96–97}}</ref><ref name=suburban88>{{harvnb|Duany|Plater-Zyberk|Speck|2000|p=88}}</ref>

[[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?'': <blockquote>Motorways and bypasses generate traffic, that is, produce extra traffic, partly by inducing people to travel who would not otherwise have done so by making the new route more convenient than the old, partly by people who go out of their direct route to enjoy the greater convenience of the new road, and partly by people who use the towns bypassed because they are more convenient for shopping and visits when through traffic has been removed.<ref>{{cite book|title=Road Accidents: Prevent or Punish?|author=Leeming, J. J.|year=1969|publisher=Cassell|isbn=0304932132}}</ref></blockquote> Leeming went on to give an example of the observed effect following the opening of the [[A1 road (Great Britain)#Doncaster bypass|Doncaster Bypass section of the A1(M)]] in 1961. 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."<ref name=chen>Chen, Donald D. T. (March 1998) "If You Build It, They Will Come ... Why We Can't Build Ourselves Out of Congestion" ''Surface Transportation Policy Project Progress''; quoted in {{harvnb|Duany|Plater-Zyberk|Speck|2000|p=89}}</ref>

In [[Southern California]], a study by the [[Southern California Association of Governments]] in 1989 concluded that steps taken to alleviate [[traffic congestion]], such as adding lanes or turning freeways into double-decked roads, would have nothing but a cosmetic effect on the problem.<ref name=suburban88 /> Also, the [[University of California at Berkeley]] published a study of traffic in 30 California counties between 1973 and 1990 which showed that every 10 percent increase in roadway capacity, traffic increased by 9 percent within four years time.<ref name=chen /> A 2004 meta-analysis, which took in dozens of previously published studies, confirmed this. It found that: <blockquote>... on average, a 10 percent increase in lane miles induces an immediate 4 percent increase in vehicle miles travelled, which climbs to 10 percent &ndash; the entire new capacity &ndash; in a few years.<ref>Salzman, Randy (December 19, 2010) "Build More Highways, Get More Traffic" ''[[The Daily Progress]]'', quoted in {{harvnb|Speck|2012|p=82}}</ref></blockquote>  An aphorism among some traffic engineers is "Trying to cure traffic congestion by adding more capacity is like trying to cure obesity by loosening your belt."<ref>{{harvnb|Duany|Plater-Zyberk|Speck|2000|p=89}}</ref>

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. Spivak.<ref name=speck />