As cities grow at an ever-increasing speed, forces of change are being unleashed on several fronts—demographic, environmental and economic. While some urban policymakers have the resources to meet these challenges, others are struggling to cope with the strains these pressures are placing on infrastructure and services.

Given the challenges they face, the message for policymakers is clear—they cannot go it alone. To make their cities attractive places to live, civic authorities need to harness the energies of all the individuals and businesses flocking into their metropolises. They need to foster the innovative spirit of social entrepreneurs who can step in with new solutions to meet demands for services and infrastructure. They must increase their political clout by forming productive partnerships with the private sector and civil society groups.

They also need to think of new ways to engage with the individuals who actually live and work in cities. After all, citizens experience transport networks, retail outlets, government services and infrastructure on a daily basis. They often have a more granular knowledge of these systems and what works and what does not work in the place they live in.

As authorities battle to help their cities thrive in the face of the global financial crisis, rising city populations and increasing environmental pressures, a "top-down" model of urban planning is no longer appropriate. If cities are for everyone, everyone needs to play a role in delivering city liveability.

In this report, the Economist Intelligence Unit analyses the latest thinking about urban liveability. Our starting-point, a global survey of urban professionals, shows that most enjoy their quality of life, and are optimistic about the future. But they are generally doubtful that their city's public services and infrastructure will cope in years to come, as urban populations swell. Policymakers will need to get better at proving that they have the long-term vision and resources to cope with the pressures that their cities will face. Here are some of the issues that they will need to consider when planning their city's future.

Keeping citizens moving. There is no denying that healthcare, education, urban design and open spaces are all vital components in a city's liveability. But our survey clearly shows that few issues are as important to urban professionals as getting from A to B and back again. When asked which policy issue they would address if put in charge of their city, most respondents selected transport—roads, public transit and parking. Policymakers must understand that from the point of view of most citizens, the basic city hardware of roads and tunnels, trains and buses ought to take priority over glorious edifices.

But urban transport planning can often end in gridlock. At best, ill-considered transport schemes can be more of an inconvenience than a help—a shiny new subway system is of no use if citizens cannot afford it, or it doesn't take them where they need to go. At worst, bad transport policy can have major implications for a city's commerce, environment and development. Schemes such as Bogotá's TransMilenio show that effective, high-volume transport infrastructure does not have to be expensive or time-consuming to build, but can have a transforming effect on a city's economy.

Designs for living: balancing community with growth In the past, whole swathes of cities were bulldozed to make way for visionary new schemes. With hindsight, many have worked well. But what was possible in the Paris of Napoleon III, for example, is less desirable in the developed world today. Citizens have more power to dispose of their leaders if they disapprove of policy, and policymakers must learn from them in order to apply more appropriate urban development. This applies in the developing world, too: the future of one of Mumbai's biggest slums, Dharavi, hangs in the balance, even though it is home to 1m people and a thriving export economy. More sensitive responses to urban growth such as the Tulou Collective Housing project in China's Fujian province show that it is possible to house rapidly expanding populations without destroying communities.

Return of the city-state? As the population of some cities continues to grow, the job of running them gets harder. Citizens continue to expect municipal governments to manage most of the machinery that makes their city run properly, but in most cities—even global centres such as London and New York—it is the state that signs the decrees and wields the chequebook on vital issues such as public transport, healthcare and the environment. Policy tug-of-wars will become more common, and city authorities will need to find a way to expand their mandates in order to deliver on their promises.

Frustrated by national and state politics, some cities are trying a new experiment, forming alliances with other cities in their own countries and around the world, to gain more bargaining power and to share ideas. More than half the world's population lives in cities, which continue to grow; it makes sense that they have a bigger say in national planning and resource policy and more power to implement their own policies. Istanbul's transport tangle is one obvious situation in which a national government should devolve powers to local authorities.

A new social contract In turn, local authorities should be prepared to cede more to citizens. The simplest way to do this is to be more transparent—around the world, citizens are combining government data with social networking technology to create incentives such as cycling maps and other tools to make city life more bearable. Meanwhile, there are more and more places where social entrepreneurship is flourishing—in Mumbai, for example, where civic services are minimal and the gap between rich and poor enormous, entrepreneurs have stepped in to establish an ambulance service which operates on the principle that those who can afford to pay for it do so.

Citizens are increasingly being asked by governments to play a greater role in society. A cynical view of this says that governments are using this approach as an excuse to cut services and save money. On the one hand, relaxing the top-down approach to city policy may take the pressure off policymakers. On the other, there is also evidence to suggest that citizens who participate in civil society have a greater degree of life satisfaction. But more can be done to ensure that social entrepreneurship is actively encouraged and supported. In the long run, the most important alliance policymakers can have is with their own citizens.