The future of transportation promises a number of advancements. Our vehicles will be electric; they will be autonomous; they will be shared. Although this future has been predicted, when it will become reality is uncertain. And so, planners are left with a daunting task — planning our communities for what is, while allowing space for what could be.
Of course there is no one solution to this challenge. But, as revealed by Gerrit-Jan Knaap, Daniel Engelberg, Uri Avin, Sevgi Erdogan, Fred Ducca, Timothy F. Welch, Nicholas Finio, Rolf Moeckel and Harutyun Shahumyan, scenario planning may help.
In their article "Modeling Sustainability Scenarios in the Baltimore–Washington (DC) Region" in the Journal of the American Planning Association (Vol. 86, No. 2), the authors predict how the Baltimore–Washington region will change under different scenarios for economies and advanced technologies from 2015 to 2040.
Their primary concern is the sustainability of the region. However, this requires them to understand how possible changes will affect not only transit ridership, greenhouse gas emissions, and forest and farmland coverage, but also the number of jobs and households.
The authors begin by constructing a baseline scenario. It projects the future of the Baltimore–Washington region using what is known — future policy changes, expected land use changes, employment projections.
With these, they make some assumptions concerning the future price of fossil fuels, government regulation of the economy, and the prevalence of new transportation technologies. Their results propose that under these inputs the region would experience growth in both jobs and households. However, it too would experience a reduction of forested area, increased emissions, and greater traffic congestion.
For comparison, Knaap and his coauthors devise four alternatives — Revenge of the Nerds, Free for All, Blue Planet, and Last Call at the Oasis — each changing the assumptions made in the baseline scenario.
The four diagrams show 15 selected key impacts as percentage differences from the baseline, which is represented by the darker zero percentage line. This line separates the "plus" or greater impact of any given indicator from the "minus" or lesser impact. As an overall shape, the smaller the footprint of the scenario, the less its impacts. The shifts in percentage within and between scenarios are relatively modest visually, despite strongly contrasting assumptions, which testifies to the difficulty of moving the needle on impacts in a large mature urban region.
Much like the baseline, the scenarios situate growth and sustainability in opposition. Scenarios either yield greater households and transportation independence (Revenge of the Nerds and Free for All) or lower emissions (Blue Planet and Last Call at the Oasis), never both.
This is complicated even further when one considers the importance of equity. Only two of these scenarios (Revenge of the Nerds and Blue Planet) decrease the daily cost of travel for low-income persons and increase house prices, the latter of which might not itself promote equity.
Here, the authors illustrate that changes in the cost of transportation will have manifold effects with perhaps none being the ideal scenario. But given the externalities acting upon our regions, it is possible that none will reflect the reality in which we will find ourselves, and that's okay.
Whether our regions prioritize growth, sustainability, or both, scenario planning demonstrates the actions within the control of planners and communities to achieve the future they envision.
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Top image: Two planning scenarios for the Baltimore–Washington, D.C., region. From "Modeling Sustainability Scenarios in the Baltimore–Washington (DC) Region" in the Journal of the American Planning Association (Vol. 86, No. 2).
About the Author
Kyle Miller is a joint Master in Urban Planning and Master of Public Health candidate at Harvard University.