Issue 567 to

The Uncertainty Paradox

Why embracing multiple futures in transportation planning will help us get the future we want. 

Urbanist Article

Transportation isn’t as predictable as one might think. It doesn’t exist independently of politics, cities, the economy, culture, climate or money — all complex systems. Demand to move around is created out of the need and desires of individuals, groups and families — not those of planners and policymakers. Transportation systems don’t grow in a linear fashion as population or jobs grow. Moreover, big “solutions” often become big problems later, as when highways became headaches after leaders failed to plan for endless desire for free or cheap roads. 

All these uncertainties notwithstanding, can’t we do better planning? SPUR thinks so. It is encouraging that some transportation agencies and others are now publicly admitting uncertainty about where things might be headed in the future and are embracing new ways to tackle that uncertainty.

Transportation plans often extrapolate from the past to predict the future: the miles driven on Highway X might go up 1 percent or 10 percent a year — or something in the middle, depending on gas prices. Train ridership on Line Y could increase by 4 percent or 8 percent a year — or somewhere in between, depending on downtown development. These “straight-line forecasts” or “projections” — standard practice for the profession — are convenient fictions that oversimplify a complex transportation system and mislead us into thinking we know what the future will bring. Transportation agencies in the Bay Area, and elsewhere, have approached planning work this way for decades. 

But relying on a single straight-line forecast limits thinking about other possibilities. Transportation planners tend to go with the safest assumptions, most of which are biased against seeing transformative change, or “disruptions.” The obvious example is transportation network companies (TNCs) like Lyft and Uber — a new model that seemingly came out of nowhere to disrupt the taxi industry, public transit, and blur industry boundaries. A decade or two ago, planners couldn’t have predicted this any more than they could predict the Bay Area’s declining transit ridership in the midst of economic expansion. Yet even when it was clear TNCs were coming, policymakers and planners were unprepared.

The history of transportation is a history of times when everything changed unexpectedly, from the introduction of the Model T to the emergence of containerized shipping to the influence and impact of the Interstate Highway System. There also have been many instances when planners thought everything would change but it didn’t (see: airships, flying cars, etc.). 

Forecasting is useful in some short-term contexts; scenario planning is a process that can pick up where forecasting fails. San Francisco’s ConnectSF scenario planning process brought community and city leaders together to come up with four possible transportation futures for the city: Mind the Gap; Building Bridges; Wild West, Inc.; and Mosaic.1 San Francisco is studying what it will take to achieve Building Bridges, a high growth scenario with a world-class, equitable transportation system. MTC’s “Horizons” process was created to study many uncertainties that fall outside standard regional planning requirements. This effort landed on three possible transportation futures to explore: Clean and Green; Rising Tides, Falling Fortunes; and Back to the Future.2 Scenario planning also inspired SPUR’s Four Future Scenarios for the Bay Area, published this summer, with outcomes that ranged from dystopic to ideal.3 These organizations have not yet completed scenario planning. But merely by embarking on the process, they have already invited a more robust and honest and productive conversation. 

The Bay Area has approximately $300 billion to spend on transportation through 2040. Allocating these funds requires making some assumptions about the future, though only some of these assumptions are likely to hold constant over the next few decades. Scenario planning has the benefit of allowing planners to test different investments and policies in multiple futures (a process known as “wind tunneling”). And we are already seeing the benefits to the region. 

A focus on what’s uncertain creates better outcomes in the end because it clarifies early on the key strategic choices, tradeoffs and inflection points still to come. Acknowledging that the future is yet to be determined allows for new creative ideas and possibilities to emerge. It reminds that we have human agency, that we can create a future that’s different from the past.



ConnectSF began with scenario and vision development in 2017, in collaboration with the Futures Task Force and conversations with the general public. The preferred scenario (Building Bridges) is now informing a subway vision, the next countywide transportation plan, a transit corridors study, a streets and freeway study, and an update to the transportation element of the general plan. See

MTC Horizons is an 18-month “blue sky” planning effort, tackling questions that are not explored in a typical Regional Transportation Plan/Sustainable Community Strategies framework. Policies and projects that make sense across multiple futures — thus demonstrating their resilience to potential headwinds — would be considered top priorities for incorporation in the next RTP/SCS. For example, the previous Plan Bay Area 2040 offered just one single jobs and population forecast for 2040. See

3 SPUR has developed four scenarios for its regional strategy work: Gated Utopia, Bunker Bay Area, Rust Belt West, and A New Social Compact. See “Four Future Scenarios for the San Francisco Bay Area,” August 2018,

Ratna Amin is SPUR’s Transportation Policy Director.

Nicole Boyer, Chester Fung and Doug Johnson contributed to this article.