Thursday, September 16, 2010

3-D girl a reminder for B.C. drivers in school zone

Toronto Star article "3-D girl a reminder for B.C. drivers in school zone" (September 9th, 2010) describes the decision of Vancouver officials to put an optical illusion of a girl playing in the road to slow drivers down. Corrections thinks this is a mistake.
The visual image of the girl is believed to be the first time a child is being used to drive home the message of the dangers in excessive speeding. In 2008, the city of Philadelphia began using virtual images of fake speed humps of white, blue and orange triangles to get drivers there to slow down.

Vancouver officials are "crying wolf." The lesson to be learned from hyperinflation or the story of the boy who cried wolf is rational expectations. Individuals are not fooled over the long run. Drivers get a signal of a child playing in the road. They then make a decision on whether or not to slow down, and if so by how much. Normally, the stronger the signal the more a driver would break. By "muddying" the signal by making it unclear whether or not it is a trick or a real child, drivers are rationally less likely to slow down. This, in turn, is likely to be a mistake.

Depicted graphically below is the ordinary relationship between signals of kids playing (balls in the street, summer days, hockey nets in garage ways) and the likelihood that kids are actually playing--that they are going to rapidly dart out into the street from behind a car, or are in the street playing already (click to enlarge).

Vancouver's optical illusions change that relationship by making strong signals mean less (click to enlarge).

Consequently, drivers break less when their signal means less--when the cry of "wolf" is less likely to yield a wolf (click to enlarge). The blue line indicates the original regime, the red line indicates the new regime, and the mixed line is the two lines overlapping.

Corrections notes that this is our own application of the "Lucas Critique" to almost all "behavioralist" policy advisements. Too often policy is suggested by small-scale experiments, when macro conditions change, given the adoption of certain policies. While experimentation yields valuable results, its generalizability outside the localized field (in which the policy it is testing has not been adopted) should always be in question.

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