Transport planning plays an outsized role in shaping the future of our metropolises. Land use and the daily activities of residents depend on transport and the access it provides. Transport only exists to serve activities people want to engage in. Growing cities naturally want to expand transport infrastructure. Because transport takes a long time to develop and deploy, and tends to be irreversible, it is worth some effort to try to get it right.
It is believed that effective planning requires accurate and reliable computerised transport models (UTPS or “four-step” models in the US, “Strategic Transport Models” in Australia), which serve as tools to predict and analyse the impacts of various transport policies and investments.
The models however are a fantasy.
Fantasy: n. “the power or process of creating especially unrealistic or improbable mental images in response to psychological need” - Merriam-Webster
These large-scale are either believed, to the detriment of all, or not believed but merely a kabuki-like, Potemkin-esque, box-ticking exercise to satisfy rules and regulations laid down in the name of scientism and used to justify the preferred actions of those in power, rather than to inform those actions in the first place.
Why they are dangerous? They place a misleading veneer of rationality over the top of single-point extrapolation. They are accepted at face value by a credulous press.
These models are almost always estimated based on a single survey at a single point in time, resulting in a single coefficient for every variable. This is fine only if nothing else changes and you have very high certainty in the rightness of your model. Casual observation of the world (cough, COVID, cough) suggests things sometimes change. So 2050 forecasts of travel demand are based on models estimated using 2010 surveys being run in the 2020s. These are no more likely to be correct within a reasonable margin of error than a random number generator. One only has to look back at the accuracy of previous forecasts.
Even if conducted in good faith (though not accurately) these models can lead to the misallocation of public funds by overstating (or understating) the benefits of transport projects. (And they are often not conducted in good faith). (The misestimation of costs is another department). When decision-makers rely on these flawed models, they may divert resources from other essential services and investments, such as education, healthcare, or social programs. This misallocation of resources can have long-term negative consequences for the communities affected.
Overly optimistic models can mislead decision-makers into supporting the wrong transport projects, projects that are not viable, cost-effective, or beneficial to the public. This can result in the approval of projects that might never reach completion or fail to deliver the promised benefits, wasting time, money, and political capital.
Unrealistic models can also contribute to environmentally harmful decision-making. By underestimating the potential impacts of a project on air quality, greenhouse gas emissions, or natural habitats, leads to projects that compromise environmental sustainability and public health.
When transport projects based on Fantasy Modeling fail to deliver on their promises, public trust in the planning process and government institutions can be severely damaged. The credibility (or what remains) of the transport planning profession suffers as a result, undermining public trust in future projects and initiatives. This erosion of trust makes it more challenging to garner public support for future transportation investments, creating a vicious cycle of skepticism and underinvestment in critical infrastructure.
Transport models are the centrepiece of the traditional “Predict and Provide” approach to transport planning. Newer thinking has moved us toward “Vision and Validate”. I am on-board with communities “envisioning” their future. But I am not entirely sure how we “validate” the future without living through it. The universe is Computationally Irreducible, we cannot know the future without running the full experiment, there are no short cuts. The same is true for the growth of cities and their networks.
Sometimes you just have to take the leap, understanding the theory and evidence about how transport infrastructure reshapes the world in a positive feedback way (more access → more development, more development → more infrastructure and more access), while recognising the randomness of life and unknowns of the world. So you should do what you think would move you in the right direction, even if forecasts cannot give you the certainty you desire. This argues for small incremental moves (leaping small distances) rather than massive ones, so your missteps are not as lethal and your elephants not so white.