Are Traffic Studies 'Junk Science' That Don’t Belong in Court?

Kristina M. Currans & Kenneth A. Stahl (2023) Are Traffic Studies 'Junk Science' That Don’t Belong in Court?, Journal of the American Planning Association, DOI: 10.1080/01944363.2022.2136735

10 Pages Posted: 20 Mar 2023 Last revised: 3 Oct 2023

See all articles by Kristina Currans

Kristina Currans

University of Arizona - School of Landscape Architecture and Planning

Kenneth Stahl

Chapman University - The Dale Fowler School of Law

Date Written: March 14, 2023

Abstract

Jurisdictions rely heavily on Traffic Impact Analyses (TIA) to predict the traffic impacts of projects and calibrate appropriate mitigations. But TIAs are also litigation tools – jurisdictions use them to satisfy courts that their land use decisions are supported by substantial evidence, or evidence that is credible and reliable. The problem, as we discuss in this paper, is that TIAs are not consistently credible and reliable. We explore some common criticisms—and a brief overview of a growing literature—regarding underlying vehicle estimation methods in practice, which demonstrates the ways in which TIAs are widely flawed. Historically, courts have not expected much from TIAs, but our analysis points towards a tipping point in which courts may begin to question whether conventional TIA methods constitute substantial evidence, suggesting an important need to innovate and adopt new data and methods in practice.

Keywords: traffic impacts, new development, traffic impact analyses (TIAs), trip generation, courts, judicial review, substantial evidence

Suggested Citation

Currans, Kristina and Stahl, Kenneth, Are Traffic Studies 'Junk Science' That Don’t Belong in Court? (March 14, 2023). Kristina M. Currans & Kenneth A. Stahl (2023) Are Traffic Studies 'Junk Science' That Don’t Belong in Court?, Journal of the American Planning Association, DOI: 10.1080/01944363.2022.2136735, Available at SSRN: https://ssrn.com/abstract=4388704

Kristina Currans

University of Arizona - School of Landscape Architecture and Planning ( email )

Kenneth Stahl (Contact Author)

Chapman University - The Dale Fowler School of Law ( email )

One University Drive
Orange, CA 92866-1099
United States

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