Every other Sunday, thousands of people spill onto otherwise auto-clogged city streets across India. For a few hours, the roadways are theirs – to walk, cycle, skate, practice yoga, CrossFit, even Zumba. Open streets days, known locally as Raahgiri Days, have taken urban India by storm and are spreading rapidly from city to city.

The open streets movement actually began half a world and half a lifetime away, in 1970s Colombia. How did it become Raahgiri Days and end up in India and hundreds of other cities? Today, in a world well past the urban tipping point, with more than half the global population living in cities, it is more important than ever to understand how such changes grow and spread.

Cities need to “bend the curve” on climate change emissions, sprawl, affordable housing and access to many other basic services. Inaction is unacceptable, and incrementalism insufficient. We need to aim for deep transformation to accommodate growing urban populations in a sustainable and equitable way. This is the goal of the inaugural WRI Ross Prize for Cities, to spotlight and celebrate initiatives that have an outsized positive impact on their city and learn what made them successful to encourage replication.

To get sustainable urban transformation right, we should understand three things.

1. Transformation Is Happening Everywhere, But Not in the Same Way

With urbanization happening at an unprecedented scale, cities are changing every day. Sometimes the very fabric of a city can morph beyond recognition incredibly quickly. Shenzhen, China, is emblematic of this. A small fishing village just 30 years ago, Shenzhen is now home to more than 10 million people and an integral part of the world’s largest continuous urban area, the Pearl River Delta.

But urban transformation is not a linear or simple process. While some cities grow and thrive, others stabilize and even shrink. More than two-thirds of expected urban growth will come from only three countries: India, China and Nigeria.

The spatial disparity of urban transformation is a key finding of WRI’s World Resources Report on cities, “Towards a More Equal City,” which identifies several cities in North America, Latin America and the Middle East where the global trend of rapid urbanization does not hold true.

Whether growing or stabilizing, thriving or struggling, cities across the globe face different challenges from each other as well. Cities’ development trajectories are the result of local constellations – prevailing political powers, regulations, finance and many other factors – that shape cities into complex, hybridized systems.

Understanding differences as well as shared experiences is an important first step towards finding an entry point for sustainable transformation.

2. Sustainable Transformation Is Needed

Today’s urban problems – pollution, congestion, inefficiency and inequality – can be described using a range of metrics; however, most don’t come close to capturing the lived experience of an unsustainable city.

For instance, you can come up with a fairly accurate estimate of the number of households without access to affordable and secure housing (330 million around the world). It is even possible to estimate the cost of congestion to most households (residents of Los Angeles lose around $6,000 a year, without accounting for carbon emissions).

But the throat ache from a morning walk through smog in Delhi, the ripple effects when cars pile up and flights are delayed and canceled because of poor visibility, those are more difficult to understand through numbers. Indeed, people who live in urban sprawl are not just unhappier while they commute, the misery extends beyond the time they spend in their cars.

While it is important to understand the big numbers such as the “weight of cities” – their consumption of raw materials, their primacy in the global economy and sustainability efforts – it is equally essential to understand and address the costs of unsustainable and unequal cities in terms of everyday experiences.

3. The Seeds of Transformation Are Often Unnoticed

Despite obvious changes in cities worldwide, it can be tricky locating the starting points of change and understanding its dynamics. Because the stakes are so high, an entire field of study has emerged in the last two decades dedicated to understanding large-scale sustainability transitions.

One of the big challenges has been to understand how big changes emerge from small changes through a range of “scaling” processes. Several iconic tales of urban transformation, such as the evolution of modern electricity networks and water supply in the Western world, show the importance of the co-evolution of technologies, institutions, markets and consumption practices.

Perhaps even more difficult than historical analysis, is the attempt to identify “seeds of change” – promising initiatives that have potential for larger impact, but which currently exist only in prototype form. Identifying these is a major focus of the WRI Ross Prize for Cities.

Even if the complexity of identifying sustainable transformations in-the-making may seem overwhelming, the ability to understand the features of promising projects, technologies and organizations will be critical to making resilient and equitable cities a reality.

In times of change, there are winners and losers. During China’s economic rise more than 800 million people were lifted out of poverty. However, while cities like Shenzhen benefited from factories, an influx of skilled workers, new construction and rising GDP, air quality in these places also declined significantly, many people were displaced, labor conditions became more uncertain, and land was often expropriated without compensation.

Cities need to generate jobs and growth for incoming populations and existing residents. But growth needs to be inclusive and within environmental limits, or cities risk creating more problems than they solve. The scale and speed of today’s urbanization, along with the additional challenges of adapting to climate change and a changing global economy, means the need to understand, encourage and guide sustainable urban transformation is more urgent than ever. We need more Raahgiri Days, and we don’t have 40 years to wait for them to arrive.

The WRI Ross Prize for Cities is a global, biennial, $250,000-cash prize competition supported by Stephen M. Ross to celebrate transformative projects that have ignited citywide change. Five finalists will be chosen in Fall 2018 and one winner will be announced in April 2019. Applications are due July 31, 2018, at 11:59 PM EDT. Find out more at wrirossprize.org.

Anne Maassen is Urban Innovation & Finance Associate at WRI Ross Center For Sustainable Cities.

Fiona McRaith is Urban Development Intern for WRI Ross Center For Sustainable Cities.