The Bright Side of Bias

Urban planners are professional imagineers. We are trained to look at a vacant lot and see homes, at a congested corridor and see safe bike lanes, at a post-industrial waterfront and see families spending a day at the beach. We are, by temperament and training, relentless optimists.

And sometimes, that gets us into trouble.

An episode of the BBC podcast Sideways explored why mega-infrastructure projects across the globe—from rail lines to bridges to Olympic host sites—so reliably run over budget and over time. The culprit? Optimism bias. The human tendency to overestimate benefits and underestimate costs. To imagine the smooth path rather than the muddy detour. To believe that this time, unlike all the others, things will go according to plan.

The planning mind is especially vulnerable.

We plan for the risks we can foresee. We build contingencies into our Gantt charts. We model traffic flows, climate impacts, construction timelines, demographic shifts. We imagine political pushback, supply chain hiccups, even a once-in-a-century storm.

And then something derails the project—because we failed to imagine it.

A global pandemic. A sudden change in government. Tariffs. A bankruptcy. A public backlash amplified by social media. The unknown unknowns. The things that were never in the spreadsheet.

Optimism bias is not incompetence. It is human. It is, in fact, what allows large projects to begin at all. If every planner, engineer, and elected official truly internalized every possible risk at the outset, very little would ever break ground.

And yet, unchecked optimism can erode public trust. When timelines stretch and budgets balloon, communities understandably ask: Who decided this? Who benefits? Who pays?

So what are we to do? Abandon optimism? Absolutely not.

Optimism is one of the most valuable tools we have.

Without it, planning would become a defensive profession—focused solely on mitigating decline rather than shaping future options and possibility. Optimism keeps us invested in the belief that cities can evolve toward justice. It allows us to picture safer streets, more affordable homes, greener neighbourhoods, and more inclusive public spaces—even when current realities fall short.

But optimism needs companions.

It needs humility. Humility means acknowledging that we do not see the whole picture. That the elegant master plan pinned to the studio wall is, at best, a draft. That lived experience contains forms of expertise no technical report can fully capture.

And optimism needs participation. The era of planners designing “ideal communities” in backrooms—presenting glossy renderings as faits accomplis—is over. The most resilient plans today are co-created. They emerge from workshops in community centres, from conversations on doorsteps, from youth councils and elders’ circles and neighbourhood walks.

Participation does not eliminate optimism bias. But it distributes imagination. It builds resilience. It broadens the field of what can be foreseen. A parent might identify a safety concern a traffic model missed. A small business owner might anticipate construction impacts invisible to a consultant forecast. A renter might surface housing precarity that aggregate data obscures.

Collectively, we can imagine more—and miss less. Projects shaped through genuine participation are often more adaptable, more trusted, and ultimately more durable. When communities see their fingerprints on a plan, they are more willing to weather the inevitable surprises alongside it.

The great urban thinker Jane Jacobs captured this beautifully: “Cities have the capability of providing something for everybody, only because, and only when, they are created by everybody.”

Optimism, on its own, can blind. But optimism braided with humility and participation becomes something sturdier. It transforms from naïve projection into collective aspiration.

The planning mind will likely always lean toward hope. We will continue to sketch the future in bright lines. But perhaps the task before us is not to dim that light—only to widen its beam.

Let us acknowledge optimism bias head-on while admitting it’s not purely a flaw, but a force to be harnessed.