More than 70 percent of the world’s population will live in cities by 2050. So cities represent the single greatest opportunity for targeted, meaningful actions that create impact on the ground, improve the quality of life for billions of people, and reduce the risks of climate change.

This opportunity was a key theme at last week’s C40 Cities Mayors Summit in Johannesburg, South Africa. The conference brought together members of C40 Cities, a group of mayors and top officials from more than 45 cities who are committed to combating climate change and furthering urban sustainability. In addition to releasing the Climate Action in Megacities 2.0 (CAM) report, which highlights the actions C40 cities are already taking, the summit discussed uniquely urban challenges to sustainability. A clear message emerged: if we are to create livable cities for a growing urban population, city leaders throughout the world must take action to provide access to education, jobs, and health services. Sustainable urban transport and smart urban design play key roles in expanding this access for all urban residents.

Three challenges to creating sustainable cities

The decisions made today will shape how the cities of tomorrow operate. Developing cities in particular have the opportunity avoid lock-in and auto-dependency, designing cities that are efficient and accessible for all. These cities must look to Barcelona’s compact urban form and not Atlanta’s sprawl as a blueprint for future development. But creating urban centers that are both prosperous and climate-resilient will require immediate action across a few key hurdles:

Increasing motorization

Private motorized transport accounts for less than one-third of trips reported by C40 cities, but contributes to 73 percent of GHG emissions. Cities simply cannot meet emissions reduction goals and curb the impacts of climate change without a plan for transport demand management that enables safe, sustainable urban mobility for all.

Traffic safety

Traffic deaths are a huge economic burden on cities. By 2030, traffic fatalities are expected to become the fifth leading cause of death globally. No city can truly call itself livable unless it can provide safe access to goods, services, and opportunities for all its residents.

Air quality

Deteriorating air quality and harmful pollution are rampant in today’s cities. This winter, for example, New Delhi’s air pollution was 60 times higher than the level deemed to be safe. Protecting human health and ecosystems means reducing cities’ pollution woes.

The answer: Sustainable solutions at scale

These challenges compound upon one another in a vicious and deeply entrenched cycle. But within these considerable challenges exists a major opportunity to decrease GHG emissions and air pollutants while improving quality of life for urban residents—sustainable transport.

Take Cape Town, South Africa. According to Garreth Bloor, the city’s Mayoral Committee Councilor and a panelist at the “Transportation Demand Management” plenary at the C40 Summit, transport accounts for 27% of CO2 emissions in the city. That’s why Cape Town implemented a robust transport demand management (TDM) strategy in 2006 that includes promoting higher vehicle occupancies and calls for the introduction of a holistic integrated transport system and congestion pricing in the coming years.

Looking beyond Cape Town, other C40 Cities are taking steps to manage transport demand while integrating transport and land-use planning. San Francisco’s new SFpark system adjusts meter rates by responding to real-time parking demand metrics, and Milan implemented a congestion pricing scheme in 2012 that has reduced traffic by over 30%. Finally, Curitiba, Brazil and Bogotá, Colombia have each built on the success of their respective bus rapid transit (BRT) systems by implementing transit-oriented development (TOD) principles along their BRT corridors

Each of these cities is now reaping the co-benefits of TDM, including improved air quality and traffic safety, reduced travel time, and an increase in biking and walking. C40 members and other city leaders can play a key role in scaling up these key solutions to urban centers throughout the world.

Leading by example: The next steps for C40 city leaders

The fact that C40 members’ sustainable development activities have doubled to more than 8,000over the last two years—including 1,534 actions directed specifically at improving urban transport—is a heartening sign. But the battle does not end there. More cities need to take action to truly scale up sustainable transport solutions throughout the world.

To that end, city leaders—both those inside and outside the C40—can take a few immediate steps to improve climate resiliency and livability through sustainable transport. In particular, they should:

1) Think holistically—Cities must integrate transport solutions into their overall economic policy and urban development plans. Cities like Bogotá and Curitiba stand as great examples of cities that have integrated transport at the heart of city planning processes, becoming more inclusive and livable as a result.

2) Act strategically—Cities that engage in sustainability initiatives should collect and maintain better data on the impacts of these plans. One way to do so is for city leaders to commit to an internationally accepted greenhouse gas accounting mechanism, such as the Greenhouse Gas Protocol or the Global Protocol for Community-Scale Greenhouse Gas Emissions (GPC). To build on this, they must also improve public access to data and foster the sharing of knowledge and best practices both within and between cities.

3) Show greater leadership—City leaders have a prime opportunity to take action and show leadership at the upcoming Climate Summit 2014 in New York City, a key meeting organized by United Nations Secretary-General Ban Ki-Moon. Leaders should use this opportunity to come forward with clear commitments for creating more livable, resilient cities—including plans for sustainable transport solutions.

City leaders are playing an increasingly pivotal role in shaping the future of their cities, their countries, and our planet. They can be at the heart of changing the paradigm of how we design and build our cities. Will they continue with business as usual? Or will they move in a new direction?