As the world continues to become more urbanized, both the total number and the percentage of urban residents will increase over time.

The world population, now at 7.2 billion, is projected to reach 8.1 billion in 2025, and 9.6 billion by 2050, according to the United Nations’ World Population Prospects: the 2012 Revision. As of late 2013, the world’s 10 largest cities (metro population) were:

  • Shanghai: 17.8 million
  • Lagos: 16 million
  • Istanbul: 14.2 million
  • Karachi: 13.1 million
  • Mumbai: 12.5 million
  • Moscow: 12.1 million
  • Sao Paolo: 11.8 million
  • Beijing: 11.7 million
  • Guangzhou: 11.7 million

The report states that the 49 least developed countries are projected to double in size from around 900 million people in 2013 to 1.8 billion in 2050.

“Although population growth has slowed for the world as a whole, this report reminds us that some developing countries, especially in Africa, are still growing rapidly,” said UN Under-Secretary-General for Economic and Social Affairs, Wu Hongbo in a press release on the report.

How does urban planning deal with such rapid growth? Is urban planning functional on a massive scale, in fast-growing cities, or does it seem to be behind the curve, unable to keep up with growth?

There are examples of both successes and failures all over the world. But where growing cities work best, you find innovative and successful planning at work.

All growing cities need to build roads, bridges, sewers, water lines, affordable housing, and solid waste systems, as well as green spaces that produce oxygen and consume carbon dioxide and air pollution. It’s a daunting task anywhere, but especially in countries that have growing populations but are always pinched for funding.

India is a prime example. By 2020, the country will have more than 500 million residents in its cities, and by 2030 India will surpass China as the most populous country in the world, with nearly 1.5 billion people. All those people will require the infrastructure of cities. By some estimates, the city of Mumbai alone needs investment of $1 billion.

“350 million people are going to get into the urbanization process in the next two decades, and India will be an urban majority country by 2040,” said Amitabh Kant, CEO and MD of the Delhi Mumbai Industrial Corridor Development Corporation.

Kahn advocates for creating all new cities, saying, “[i]f you don’t create new cities, every existing city will be a slum.”

That will cost a lot of money, but it’s also forward thinking, and thinking big.

Where urban planners have been most successful in building the infrastructure needed in a modern city, a few patterns are apparent. Planners and cities must, to succeed in addressing the needs of a growing population:

  • Think big and creatively.

  • Embrace a regional approach to development.

  • Limit sprawl and increase densities.

Bus rapid transit is an example of a creative idea that’s functional and cost effective.

When properly designed, BRT can equal the capacity of a rail system at a fraction of the cost, be built in existing transportation pathways, and be operational in less than three years.

Jaime Lerner, former mayor of Curitiba, Brazil, was instrumental in developing the BRT.

“I am absolutely convinced that it’s possible to carry a lot more passengers with bus rapid transit than with a subway,” he said. “And in a much more pleasant manner.”

When building solutions like BRT that can serve an entire metropolitan area, establishing a regional planning authority is crucial. Coordination of projects and services demands that multiple stakeholders cooperate.

“Regional Planning Authorities are probably the agencies which are better equipped to help with the physical and strategic plan of the metropolitan space,” wrote Mila Freire, senior adviser at the World Bank, in the report Urban Planning: Challenges In Developing Countries.

According to Freire,  regional planning is necessary so that “the region or space is seen as a dynamic entity shaped by the vision and desires of the different units that form the metropolitan space.”

She highlights New York and Barcelona as having important metropolitan strategic plans.

Planning is required to counteract sprawl development. Without effective urban planning, informal, low-density development dominates and consumes available land, resulting in a greater ecological footprint, less efficient infrastructure, and higher costs for roads, sewers, and water service.

In a competitive world, cities must embrace planned growth or risk being left behind in the global marketplace. Cities that develop successfully have stronger economies, as they’re able to integrate more people into the economy, increasing growth. Those cities will then have more money to fund further development, which attracts more business, leading to further growth and a higher standard of living.